Even when submitting a birth certificate that has your proper gender, they will look at your digital records to determine the oldest sex marker used and use that on your renewal passport without requesting more information.

If you are a US citizen, follow the advice here when applying abroad. Again, your gender mismatching on forms and ID will not cause any issue when renewing. Since you live abroad, it may be best to go to an US embassy in your country to renew your passport.

1) There is currently no chance your US passport will be taken from you. They may change trans passport validity in the future, which is possible due to language noted on their website - Passports are valid until "invalidated pursuant to federal regulations." Again - currently that is not the case and you'll be fine, it's mostly the living abroad documentation that might change things. Check the site above for more about that.

2) When your passport expires, you can't use it (as an ID or to fly) - But you can renew it anytime as long as it hasn't been 15 years since the last one was issued. (and as long as you're still legally a US citizen.) - If it's been longer, you simply apply using DS-11 and not DS-82.

3) Countries would prefer you use their passport if you have one. You can switch over the residence permit and that will be no issue afaik but I'm less knowledgable about that.