Child guardianship and mandatory military issues are problems created by the patriarchy. Dismantling the patriarchy is part of feminism, and feminists work toward this in many ways.

I do see men's rights groups advocating for child guardianship issues, and that's great, they should fight for that and feminists should (and do) support them, but why should the responsibility to fight for this be solely placed on feminists?

Mandatory military service is just fucked up and I think everyone should be fighting this, including men's rights groups and feminists. But again, not an issue that primarily affects women or feminists, so why should they carry the brunt?

Female-focused education, by which I assume you mean educational opportunities created to provide equity for women, are no different than other equity-creating opportunities. If there are systematic issues that prevent a certain group from accessing the same level of education/jobs/whatever, then rules can and should be made to assist those people to have equal access to those things. That's equity, and it builds the path to equality. (Of course, the US just got rid of all of that, so nothing to worry about for US people who have an issue with equity)