So far

It seems like most, if not all, the multithreading stuff is dealt with. Again, PC ran finely, and even on Android it runs smoothly, no errors and even warnings (although one time it crashed with some ArrayList out OutOfRangeException, but it hasn't come up again since then). In fact, it runs so smoothly it's suspicious. Maybe I'm underestimating modern smartphone power.
I've finished integrating scene2d in libgdx (I haven't mentioned it before but I'm using Java and libgdx, it's great) in the things programmed so far, so maybe it'll be easier to program more stuff later.
So now that multithreading seems to be out of a way, it seems like a large burden is off my shoulders.
Plans now:

1. Integrate basic physics with Box2D
2. Create a contollable player
3. Multiplayer support

I might be getting ahead of myself, especially with #3. I have experience with the first two so they shouldn't be a problem. #3, however, not really.
Also, I've heard that announcing what you're going to do in the future kills your motivation or something, so there's that.