I've hired ppl who literally specialize in Japanese/American contracts to write contracts up. I've tried multiple publishers multiple times. I've talked to experienced translators and licensees for advice. it's been over a decade of trying, like WHAT GIVES.
one thing that was a surprise to me as an american abroad is how many businesses there aren’t actually in the business of doing business. opportunities? sounds sus, they don’t know her.
Is it not allowed to reach Japanese artists directly? Would it be frowned upon to go over the editor's head? With that said, it's entirely possible they have to frequently deal with "I Love Anime Big Tidies" people who think that them being Americans and liking anime is enough to become publishers.
See if you can get Domu, I’m tired of it being out of print!