I know for a fact that every Muslim whomsoever has the Shahada on their tongue will enter paradise. Would that also mean that a Muslim who is in a haram gay relationship/marriage and continues to remain practicing Islam by praying, fasting, repenting, etc. still end up in heaven despite disobeying Allah as they indulge in homosexuality?
Yes a homosexual muslim practicing islam CAN still enter paradise,
So everything is forgivable by Allah, except Shirk (association of others with Allah in worship). Thus, by being Muslim, everything is forgivable by Allah will. Shirk and Kufur are alike.
Surah Zumar 39:53
Say, "O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah . Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful."
Other verses I found
Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills. And he who associates others with Allah has certainly fabricated a tremendous sin. (Quran 4:48)