bro leaving islam has no punishment, scan quran line by line you wont find a punishment for converting from islam to any religion.
as for the sexual relationships, there is more to discuss more than the nature of someone who suddenly felt attraction to same sex, or even born with it. note that quran didn't judge homosexuals with any kind of label, quran acknowledged the act itself as sin, exactly as adultery. ofcourse i cannot convince you that it is a sin, some consider it natural thing. some consider it a sin. what matters to me is that we accept people from all backgrounds and religions no matter what they did or do. i.e., i stopped hating anyone just because they sin differently.
As I said above, that is enough for me as it is an immoral act to do so.
That's good, but calling their actions sin not because of reason, but because of a book is still problematic.