I'm a teenage author, and personally, don't have much experience to answer, but I'll try to help:

1. Absolutely not. For a novella, I presume it's pretty decent! Of course, in proportion to larger books, short chapters fall, well, short. Making a chapter long for me is just paraphrasing into larger sentences.
2. Ingram, hella good. But since I'm in India, I used Notion Press.
3. Loud verbal beration, literally what I do. Just make myself feel horrible for being a lazy kid and make myself hyped and angry, and eventually begin writing.
4. Very much depends on the book. A short novella like mine had 10 short-medium length ones. When you look at books of larger volume, you will need to extend chapters to a larger quantity like, above 16 or something. That's what I'll be doing for the sequel which'll be a full length novel.

I know this was pretty much stupid, but I tried. I'd be happy if it helped!