YouTube Comments are like... diarrhea. I for real found a video of an opera singer doing a recital with comments about her "rack".
If you can, maybe ask the person that posted the video to turn the comments off.
The only "good enough" you have to live up to is yourself. You don't have to look exactly like a super-skinny anime character because you're not a 2D drawing - no matter what you do, you'll never be 100% like that character even though it can be fun to try. That's what's important - fun
. Do what's fun for you. If you don't want to go to the gym more, don't - as long as there's no medical concern you don't even have to go at all if it's not something you get enjoyment out of.
I think you look totally adorable. I wouldn't comment just for the sake of it if I didn't mean it. Normally I don't comment on how people look, just the costume, but since you were getting negative comments I figured I might as well help balance it out.
Edit : Also, I remembered that just today my mom found some of the rude comments my younger sibling had made on some web-sites - and it's not like these were hidden from future employers. It could very well come back to them.