lately I’ve been questioning free will and if it really even exists

This is the ultimate question to be grappled with, imho. If there is no free will, then we are all merely machines. And, if we are all merely machines, then the likelihood that other 'machines' (i.e. machine-learning algorithms and AI) overtake the human race is but a matter of time.

Also, if there is no free will, there is no morality -- how can an individual be held responsible for 'bad actions' when he/she had no choice in the matter? How can Thanos be 'evil' for wanting to annihilate half of all the beings in the universe?

Personally, I do not find the "there is no free will" argument compelling; however, I doubt I could ever present an adequate 'proof' that free will exists (other than the notion that our own conception of morality exposes something within ourselves that deeply begs the question -- similar to Descartes' "I think, therefore I am" -- I have an innate sense of right and wrong, therefore there must be some reason I have that sense, and a lack of free will would violate that reason).

However, like all things, that sense of right and wrong can become corrupt, can lose its bearings, can end up pointing an individual in the opposite direction. The fact that we possess a moral compass strongly suggests that we are free to choose one direction over another -- even if that compass is subject to various corruptions and/or misalignment or drift.