There is an option to change the font from settings(it redirects you to theme app), although it is a bit quirky to say the least. You see font samples mostly in Chinese at the first glance (after you click on the specific font you get normal characters preview) and there is a some weird system the requires membership (?) or payment for these. I tried some and font actually changes, although I reverted back to stock one for the time being. When I'm back at work I'll ask my Chinese colleague to guide me through that stuff as my Chinese skill is non existent.
You've always had problem with the phone/brand. Why didn't you sell it then? Do you have masochist within you?