Nice first (and last) post.

I like this too, very charming !
The things that doesn't seem to work for me are the small dithering parts you made on the tree, try keeping it plane for the shadows.
Also, I had to observe it for like 5 minutes before realizing these were brains at the end of the branches. I thought there were like big fruits or something.
I really really like the mechanic 16x16 tiles, you can make a few 32x32 blocks for some variety as well

You just took Ryumaru's edit and edited it a bit, wtf dude.

Hm, looking at it closely, I'm really not sure he did that. He may have been heavily inspired but I guess that's the purpose of an edit.

I really like were you've got so far ! Tho I agree with seiseki on the black BG. White is defenitely an option, especially considering the nature of your music, but I do think you can find somethin that'll fit better.
The one you posted before your last message are really good too, not sure why. It feels less muddy, kind of lighter.

Hey ! I'm on mac as well and I've been using photoshop forever and never had any problems considering pixel art. I would even say that it has nearly all the tools you need for PA. I don't see how it's a problem that tools ain't designed for pixe art since they do the job.
You can animate in photoshop as well (depends on the version but if it's recent you should have it). I'm not a photoshop nor color limitations expert but looks like photoshop is pretty ok considering color count and palettes as well.