Glad to hear you're enjoying it! I made Dungeon II with the specific goal of seeing how much I could squeeze into 4K (same size as Adventure and Haunted House). I wanted to see if Atari could have done something like it back in the '79-'80 time frame. It turns out they could have, which is a little sad when you think about what could have been (Looking at you Swordquest).
I test my stuff on a real 2600, Stella & z26. As far as all the emulation based hardware that is out there now, they all seem to have compatibility issues for varying reasons. Sometimes the community comes up with firmware fixes, etc. to help, but for the most part I consider it to be the manufacturer's problem to resolve.