My son went into a twin bed (with side rails put on the outside side, the other side pushed up against the wall) a little earlier than that and he did GREAT. He was an early walker and a big time climber, and he was climbing out of the crib around his 1st birthday. I put him on his crib mattress on the floor for a short while, but that just didn't work very well, as he would roll off it (which woke him up--didn't hurt him, but woke him, and thus me, up). So we just put up a twin bed and he went right into it with no problems and went to sleep at night easier than he ever had for months.
As far as the potty, I would let him do what he wants. He seems very intent on doing this right now, so go with it. If he stops being interested next week, so be it. But for now, even though you have to stop whatever you're doing to help him, it's less diapers to change, right? If you don't mind the extra work to help him each time, then just go for it all the way. What is important is that HE be initiating the potty use and letting you know/asking you to help (if/when he needs it). Eventually he will not need you as much, lol. But in the interim, he is learning to follow his body's cues and YOU will have less diaper expense, lol. My son was fully trained at two and a half, so it definitely is within the realm of possibility at his age. And he will grow so fast, that before you know it he will be able to reach what he needs to with the proper step stool (unless your house has industrial height toilets, lol). And even then, he will need help in public bathrooms, b/c THOSE toilets ARE tall! ;)