He sounds about as reliable as a cardboard boat. In my opinion, you need someone who matches your level of commitment.

I’d say this is almost worse than a romantic break up! This is someone you trusted to help execute your artistic vision; which is really sad because it sounds like somewhere in that black hole of a heart, he might have some excellent artistic insight.
To answer your questions directly:

1. Should one tolerate anything for great art and literature?

To me, art is a sacrificial process, more specifically there is always “something” given by the artist. Sometimes these conflicts in life can be a source of inspiration, but if it is difficult to put that inspiration to the page, what good does it really do?

2. Is there a way to keep his attention on the work?

I’d rely on the evidence he has given you in the relationship so far. As an artist has he treated you with the respect you deserve? As a woman? To me, it sounds like the answer for both is no.

Final question I’ll answer from you:
“Any advice?”

I’m going to be a little snarky, and say don’t listen to yourself. There is no reason to believe this is the only writing partner you will ever have; also, there is no reason to believe this is the best writing partner you could possibly achieve!

I would take on what others have said and apply actions speak louder. his actions seem clear as much as a disappointment it may be coming from a "trusted" friend. Or someone you trusted as a friend. Maybe explain if he puts his sex drive away during and around your work together you can carry on but otherwise I just see the same pattern repeating. Unless of course there is some external factor triggering his recent behaviour to suggest it was not part of a general or larger life pattern. There are a lot of illustrators too looking for work I would think

You sound like the type of person who has the talent to write on your own, and likely thrive at it. My personal opinion, not knowing more of the situation, is to strike out on your own and make your own stories happen!

I understand how it hurts to have this sort of thing happen, but perhaps finding another writing partner who isn't motivated to have you as a partner because of their need for sexual gratification is another option? But I think you can do it solo and likely produce superior work. Believe in your own strengths!