The muscle will go away with time. Well, to some extent, extent which depends on how your genes are. Yes, your body fat percentage is likely to go up. But muscle won't "turn into fat". You'll get smaller-looking, and are likely to lose weight. The only way you'll gain weight is if you eat too much. Metabolism goes down, after all.
A low-calorie diet, of course, will help you be small. But don't overdo it. HRT changes need nutrients to happen properly, just like a normal puberty. So you need to eat well and sufficiently. Of course, bananas and pasta won't do at all. You need a variety of nutrients, and they can't give you that. On top, if you take spironolactone, the antiandrogen most widely used in the US, you're likely to have problems with high potassium levels. And bananas are a high source of it.
As for your face, uhm. Sometimes, just the subtle changes from HRT make a surprisingly big difference. Apart from that, haircut, proper eyebrow shaping and make-up usually get you to at least an acceptable point. That can be a little annoying as it's a bit like disguising yourself, but there's always the option of managing like that whilst saving up for FFS.
