The Will of a 2 Year-Old vs. The Determination of a Mommy

Is it just me or are 2 year-olds unbelievably strong-willed? I know, I know, everyone says, oh yeah, that's a 2 year-old blahblahblah; but I can't believe their little brains are capable of the maniacal power games that Henry seems to play.
Picture it, nap time today: Henry spent two hours (this is not an exaggeration) jumping out of bed, running down the hall, and then standing in front of me jumping up and down, shrieking, grabbing toilet paper, flushing toilets, and doing anything else he could in what I can only assume were attempts to rile me up. In true "Supernanny" form (I'm a devotee), I did not engage. I ignored for a while (which usually, eventually, works--in that Henry gets tired/bored and eventually just goes to sleep). In the past week, my next step has been to lock him in his room--something I was initially against (what do I do when he can break out? And isn't the point to get him to learn the rules?). But several friends told me this worked for them, so I tried it. However, my little devil learned how to break the baby lock in less than a week. I locked him in today, hoping that he wouldn't bother fiddling with it; and by the time I was down the hall he was running after me, lock in hand. Finally, I began to silently escort him back to his bed. Again, I did not engage: After I put him back in bed the first time, I said "It's time for rest, honey." The next 247 times, I kept silent and made no eye contact. I even tried to make the walk back to his room as boring as possible--walking slowly and quietly so Henry couldn't run. But this went on for two hours, people. TWO HOURS. Henry never got upset, pitched a fit, or cried. He was completely content the entire time.
I find this kind of thing so difficult. As a parent, you start questioning yourself--at least I do. Am I doing the right thing? Is this ever going to work? Even if it works today, am I going to have to start all over with this tomorrow, and the next day, and the next day? It's especially hard when you're alone or (most difficult) when you're with someone who does not support you. My mother, God bless her, is thoroughly, completely, head over heels infatuated with my children; and as a result refuses to enforce anything resembling a rule. She also questions me (that's putting it mildly; it's really more like an active criticism at best and a complete tantrum at worst) when I'm attempting to set limits with Henry. So, when I'm with Grandma Margie, it usually goes something like this:

Me: Henry, it's time for bed.
Henry: Wah!
Grandma Margie (to me): Are you sure he has to go to bed now? He didn't eat enough dinner. He's been sick! This is a new environment! He's excited to see his grandma! Can I go in there and talk to him? The fan is running in his room, and it's keeping him awake! The room is too warm! The room is too cold! Do you think I should go in there and sing to him? He doesn't like the color of the room! Don't you think I should go sit with him? I'm going to go sit with him.

This continues until I either give in or tell her (usually loudly) to STOP, in which case the whole thing starts again within a minute if Henry is continuing to complain. The point is, when you're a new parent (again, at least for me) and you've never done this before, and you're trying to raise your kids right, it really sucks when other adults aren't supporting you.
Anyway, I'm proud of myself today because I stayed calm (deep breathing helps), did not engage, and kept repeating to myself, "I WILL out will this two-year old!" Eventually, Henry got tired and instead of popping up and running down the hall after I put him in bed, he got up at a regular human rate and walked down the hall. Silently celebrating a chink in his armor, I carried him back to bed; and he immediately started to get back up. I put my hand on his belly and quietly said, "We don't have to do this, honey. You can relax. It's okay. It's time to rest now, but we'll play later." He went to sleep.
I'm fucking exhausted but proud of myself.