Some of the feats listed to Thanos advantages has occurred very few times and some is linked to his technical equipment. I'm not claiming to be right, I'm sure some one has read more of Thanos than me and can correct me. Here's my view on Thanos feats:
Teleportation
Thanos can teleport, but only "short" distances and this is a invention of his, not a natural ability. He was banned by Nebula to "forever float in the depths of space" in the IG series, shouldn't he have been able to teleport himself away if it were a natural ability? Of course, Nebula had the Infinity Gauntlet and could have removed that ability, but I have never seen Thanos use the teleporter as an offensive weapon.
Matter manipulation
He turned a skrull into stone, but has since then never been seen to use the ability since (remember, from what I know!). This feat was used when Thanos was young as a character and his powers were not decided. He has had plenty of opportunities to use this skill and been in need of them.
Mind powers
Yes, he has engaged Galactus, and for a moment he had him on the ropes. But, not due to his psionic powers. The world eater stated that Thanos tricked him:
Galactus: "Damnation! You sought to seduce and violate me, Titan!".
When Galactus then assaulted Thanos he fled the battlefield. And as of resisting Moon Dragons mental probing, it was stated by Moon Dragon her self that she could not read the minds of any member of the Infinity Watch, which the Titan was secretly a member of.
Thanos: Can you read Adams mind from here?
Moon Dragon: No. Nor can I read it when I'm standing next to him. Can't scan any of the Watch for some reason.
Thanos: Because when Adam was God he decided he didn't want you to. Smart lad, always thinking ahead.
Moon Dragon: Speaking of looking into minds... I can't see into your's either.
Thanos: Of course not. I am Thanos
The part about Nate Grey I'm not familiar with. I do know that he toyed with Drax, but any "real" attacks he's mustered has been with the aid of the Soul Gem or a third party (Moon Dragon, Prof X).
About the physical strength, I would just like to add that when he beat the Surfer to death he wore the IG, so we can't know for sure that this feat was of his own strength.
About the fight then; if Thanos would choose to engage Maestro in a hand to hand scenario he would get beaten around. People have landed punches on the Titan before, why wouldn't Maestro? I don't think it would be a very entertaining fight though, seeing as the would fling each other around several miles/kilometers and then spending vast amount of time trying to find each other.
Maestro has impressive strength and it increases with his rage, but in return he looses his intellect, doesn't he? I don't think he could be in a "super-mega-mad-as-ever-before-woho-I-just-reached-the-200 000-class" state and still be able to think rationally. Then it would be an easier match than previously to outsmart him and some how immobilize him.
Lastly, the one reason Maestro looses is Thanos' Power Cosmic.