I'm going to mainly disagree with you.
1/ Is there no good gay romance written by (straight) women?
Brokeback Mountain, The Front Runner, the Nightrunner series, and The Catchtrap come to mind as good gay romance stories written by women.
2/ The Seme/Uke tendency of (mostly) straight men fucking chicks with dicks is something that gay men write as well. The fantasy of straight men fucking other men is very popular even in porn for example Broke Straight Boys.
3/ Yaoi developed in Japan quite separately from the development of m/m in North America. Here it came out of fanfiction culture, largely female but not exclusively, who write romance stories about their favorite characters. M/M represents male with male, M/F represents male with female, and F/F represents female with female. Quite often you'll see men forced into hyper-feminine and hyper-masculine roles but that's based on how heterosexual romance tends to be written: Mr. Darcy is older, wealthier, higher social status and smarter than Elizabeth Bennett. Women will write X-Files fanfiction where Scully is completely subordinate to Muldaur as well as fanfiction where Krychek is completely subordinate to Muldaur.
4/ Homophobia doesn't come out of reading YAOI. It doesn't particularly get rid of homophobia either. It's no different from straight men watching "lesbian porn".