First off upon reading the passage it appears Caedus couldn't even sense Luke's presence in the Force even when he had prior warning. This further supports Caedus's utter inability to compare to Luke as a force user who has also as I've mentioned casually pinned Caedus to a chair without gesturing or making any movements at all. Another good example exemplifying the gap between Caedus and Luke is force users is this little scene.
"He felt the hot sting of the thorns pumping their venom into him. His hearing faded and his head began to spin, and he saw Jacen, one hand still raised to keep Luke pinned, sneering and taking his time rising. Bad mistake. Luke raised his lightsaber, slashing through the thorn bed as he sprang." - Inferno.
Even when Luke is trapped in a Vong torture device being poisoned and his sense being dulled Caedus is incapable of holding him in place with the Force.
Putting that to the side for now let's address the rest of your post.
Luke not only had a bad knee but a chest wound from his duel with Lumiya.
"Luke stumbled back, his chest filled with fire. Jacen had caught him on the barely healed scar from his first fight with Lumiya, and now his breath was coming in short painful gasps." - Inferno.
And not only only was Caedus clever with his environment he was completely familiar with it as well. Given this fight takes place on neutral ground he won't have the same advantages he held in his fight against Luke.
It's also specifically mentions that Caedus's pain empowered him making him stronger and faster.
"But Jacen thrived on pain, fed on it to make himself stronger and faster." - Inferno.
Also you should make note that Caedus is on the defensive for the entirety of the fight and attempts to flee as soon as he is able to disengage with Luke.
"Jacen scrambled to his feet, barely bringing his weapon up in time to block a vicious downstroke." - Inferno.
"Except Jacen was sliding backward, one hand extended behind him, using the Force to pull himself toward a tendril-draped rack in the far corner of the torture chamber." - Inferno.
"They exchanged perfunctory attacks as he tumbled past, then Luke was alone in the corner, watching the green column of his nephew's lightsaber move toward the door. Jacen was running." - Inferno.
"Then gave ground and vanished behind the green ribbons his lightsaber was weaving through the darkness." - Inferno.
It should also be noted that whenever he actually does engage Luke directly, even hindered as Luke is during the entirety of the fight, he gets trashed.
"Landing an elbow smash to the temple that dropped Jacen to his knees. He brought his own knee up under Jacen's chin, hearing teeth crack-and relishing it." - Inferno.
"He landed an elbow and felt a bone in Jacen's face shatter." - Inferno.
"Luke slammed an elbow into Jacen's ribs, but it was like hitting a permacrete wall. Instead of continuing to fight, he accelerated into the spin, using the Force to hurl them both into the nearest wall. Jacen hit first, his skull clunking hard into the durasteel. The garrote loosened a little. Luke dropped his lightsaber, bracing one hand against the other so he could use the strength of both arms to hammer his elbow up under Jacen's chin. The garrote went completely slack." - Inferno.
This is despite Luke growing progressively more and more injured by Caedus's tricks and the aggravation of his prior wounds.
"Luke stumbled back, his chest filled with fire. Jacen had caught him on the barely healed scar from his first fight with Lumiya, and now his breath was coming in short painful gasps." - Inferno.
"He felt the hot sting of the thorns pumping their venom into him. His hearing faded and his head began to spin." - Inferno.
"Holding his weapon with one hand and driving a Force-enhanced punch into Luke's ribs with the other, striking for the same place he had kicked earlier. Luke's chest exploded into pain, and he found himself croaking instead of breathing." - Inferno.
"Jacen kicked at Luke's legs, catching the side of a knee. Something popped and Luke felt himself going down." - Inferno.
"A tremendous crash sounded from the illumination panel, and the chamber fell instantly dark. He rolled opposite the direction he had just been moving, but wasn't quick enough. The fixture smashed into his head and shoulders, slamming his face into the deck. He heard something crunch in his nose and was instantly choking on his own thick blood." - Inferno.
"Luke had barely started to turn before a loop of thin tendril slipped over his head and tightened around his throat, oozing toxin and cutting deep into the flesh. The wound swelled and burned as if it were on fire." - Inferno.
Hell even with his amped physical strength Caedus can't even keep Luke from forcing his blade to cut into his shoulder.
"Beating his nephew's guard down so far that Jacen's emerald blade bit into his own shoulder." - Inferno.
So to sum it all up we have an amped Caedus fighting an injured Luke in a setting he is intimately familiar with and still being on the defensive for the entirety of the duel and attempting to run away whenever possible, not to mention Luke being distracted by the presence of Ben during the entirety of the fight.
""Wait!" Ben cried from behind him. "Let me do it!" Astonished and appalled, Luke put a little too much weight on his injured knee-and fell as it buckled. He rolled beyond the reach of Jacen's lightsaber and looked back across the chamber. Ben was still strapped in the Embrace, but he had summoned the vibrodagger off the floor and was battling to cut himself free of the chair's lashing tentacles. Luke shook his head. "I don't think so, Ben." "You have to!" Ben insisted. "I deserve it!" "Deserve it?" Luke returned to his feet, far angrier with Jacen than he had been just a moment earlier. "To kill someone?" "You don't understand, "Ben insisted. "It was my fault. If I don't do this..." "I said no, "Luke interrupted. How could Ben believe that he had a right to kill someone? "You're very confused, Ben. We'll talk about this later." Giving his son no further chance to argue, Luke turned back to Jacen, who by now was almost free." - Inferno.
His son's presence is even used by Caedus to maneuver him into a trap.
"Luke pressed forward, angling toward the Embrace to keep Jacen away from Ben. Jacen fought his way over anyway, placing himself squarely between Luke and the chair, then gave ground and vanished behind the green ribbons his lightsaber was weaving through the darkness. Luke Force-leapt after him, knowing that this Jacen- the Jacen he had caught torturing his son-would not hesitate to take Ben hostage... or to kill him. Luke landed half a meter in front of Jacen's lightsaber and quickly beat down his nephew's guard-too quickly. When he did not glimpse a face in the light of his own blade, Luke knew something was wrong and stopped. Which was exactly what Jacen was waiting for, of course." - Inferno.
To address your powerscaling argument I would actually not disagree with you that RotJ Luke is a match for RotJ Vader as a duelist. I also would say that Galen being around that level as a duelist is accurate as well.
Actually, I do. If RotJ Luke was as merciless as, as familiar with the area, and as powerful as Caedus along with holding the same advantages over Luke that Caedus did during the fight, not to mention being amped by his own pain, I believe he could replicate such a performance.
Given you have yet to prove such I'd love to hear why you think that would be.
He withstands illusions on Kashyyyk similar to the ones Luke faced on Dagobah. While we don't know if Luke by Inferno would or would not have I'm simply saying that Galen has experience with dealing with illusions.