Hmmm...what's the rest of his day look like? What time does he wake up? What time does he go to bed? I'm wondering if he might do better with one good nap, but perhaps timed better. 2 PM sounds a little late, unless he starts his day at 9. Putting him down for 2 naps when he isn't tired enough gives him enough energy to scream the house down, and putting him down for 1 nap too late can make him overtired enough to do the same darn thing. You know your baby best, though...if you really do feel that he does best with 2 naps, keep at it. Stay consistent, and he'll come around. Toddlers are notorious for throwing weird curveballs with sleep, and sometimes the best thing to do is nothing at all until it passes.
As for the tantrums, are you giving him a heads-up that bedtime will be soon? For example, "after we do x, then we go night night." Tyler gets irate when I interrupt him or just whisk him off to the next activity with no warning, so that might be part of it. And don't forget the power of choices. The tantrums may be a reaction to having to do something he doesn't want to do, ie, a control issue. Do you offer choices throughout the day? You can also offer them at sleep time, like letting him choose between 2 books to read or 2 stuffed animals to take to bed. Even though he may not make a choice, sometimes just having the opportunity to have some control is enough. Neither of these are overnight fixes, but with time, that may defuse the problem.
When he does have a tantrum, what happens if you give verbal reassurance from the door? When we do this with Tyler, we use the exact same phrase over and over..."night night, Tyler." If it isn't working, we'll pop in, lay him down, use the phrase, and leave straight away. We do this over and over and over, and eventually he calms down. We can't stay in the room either, but for the opposite reason...he peers through the crib bars and giggles the whole time. :roll:
Hang in there!