Can a Muslim still be a Muslim and eat pork, drink alcohol, neglect to pray or ever go to a Mosque, fail to fast during rammadan, never go on Hajj, be openly homosexual,
Objectively definitely not. We have only ONE objective definition of "Islam" ie "submitting to the will of Allah" as laid out in the Qur'an. A "gay-friendly", wine-imbibing "version" cannot therefore be objectively accepted as equally warranting the name "Islam" as a gay-unfriendly, wine prohibiting "version".
When does a Muslim stop being a Muslim; when the Muslim stops self defining as a Muslim? This is clearly wrong.
Not according to Hassan Radwan. Actually HR rountinely contradicts him on this since, in contravention to his words to Robert Spencer, he does often take issue with Muslims' "interpretations".
Can Islam be anything other that what it defines itself to be?
No
The word "Muslim" is not a catch all term, it is for identifying a specific person with a specific set of beliefs. If you stray from the path of a non-evolving rigid dogma then you should heve the courage to call a spade a spade.
I think "Muslim" is so core to the identity of those who regard themselves as such that without it they do not know who they are. So they cling to it like a shipwrecked person clings to a fragment of rotting flostam even though they know it stinks.