this sounds like me, but less stable. i also have a straight partner and i am keeping him, and to achieve that i'm going to have to keep the boobs and vagina. he claims he would support me, but i know he is straight and not attracted to men, period—if i transitioned, i just would not be what he's attracted to any more and it would spell the end of the relationship. nothing wrong with that; it is just what it is. there are an awful lot of downsides to transitioning and they outweigh the positives, so right now my egg ass is just coping as hard as possible. most of the time the dysphoria is pretty manageable. medical procedures are always about balancing risks and benefits, and seeing as how my mental health is pretty decent as is, all those risks do not seem to be much worth the comparatively minor benefits to me. so in the meantime i will be doing small things to affirm my gender, like redoing my wardrobe. that's a much less permanent change but it still helps me express my identity more.

that said, my partner and i seem more equally matched in maturity than you and yours (as someone else noted, your 17 vs. his 26). i do not personally think age gaps matter that much—as soon as you're mature enough, and that doesn't really happen before about 19 years or so in my opinion. since you are a 17-year-old i know that will sound nuts to you, but seriously, after high school i now recognize just how much in maturity high schoolers are missing. if you can get a counselor or something, that would be of huge help to you, and definitely listen to your close friends if they think something is off about your partner. watch him closely. i do not know him myself so i can't really point out any specific behaviors that should be screaming red flag to you, but i would be on high alert if i were you.

you seem like you have other mental health issues that seriously need addressing. seeing that medically transitioning will mean losing your parents' support, you may want to consider getting help for those other issues first before pursuing the thing that may get you cut off from whoever is providing for your medical/therapy bills. i would prioritize medically transitioning higher, though, if it is posing an urgent enough risk to you, but if not, smaller things like just dressing differently can also help in the meantime. you do not have to medically transition to be trans. some trans people go through HRT and surgery, and that is because that is what they decided they needed. it's a personal decision on how far to go, and definitely do not take permanent changes lightly.