He can lift at least 4000 pounds, and if he an lift that much, he could punch that much. A normal human being can put easily 800 pounds of pressure into a good kick, thats strength, but mostly skill. The Chief, he has a lot more. His suit is controlled by his thoughts. You can think of a move, easily, physically doing it, that's harder. The chief, he does everything he thinks perfectly most of the time, it's how the suit works. He can easily punch 4000 pounds of pressure. 2 tons = 4000 pounds. The fact that he can lift over a ton is well known fact about the MC and people who know him.
I'll say this, the MJOLNIR armour, is fast, it's strong, and it's powerful. When unenhanced humans tried to use it, it's speed was so much more than the average person can handle that the movement tore muscles and ligaments from the users bones and in the end ripped them apart. Normal people can't use armour. It's too fast.
How smart is the Chief, and Cortana? Well, he had a supersonic jet after him that fired a missile. He was fast enough, and smart enough to dodge the missile and survive, with still plenty of stength to climb a rope or something like that. I forget the exact detail of what he climbed.
He can flip a Warthog with his arms almost straight out to either side. Do you have any idea how akward that is? No one can lift near their max in that positoin, he flipped a hog that weighs over 3 tons without much effort. Granted, it wouldn't be the full three tons, the position of his arms show he's strong enough to lift tons... Even without his armour on and with boxing gloves on, when he was 15, be shattered a mans face and jaw with one hit.