Ardent atheist here. No, we don't have free will, because of legal, social, & cultural constraints either self-imposed, or imposed upon us. I think most humans have an innate sense of right vs wrong, of justice and fairness. Many animals species do too.
I do not believe that being religious gives you a sounder moral platform than being an atheist. Atheist or religious, both have proved to stretch the meaning of what is right and moral. Being religious may have imposed rules written down but atheists are a bit freer to decide for themselves what is morally correct. Even though I'm an atheist, I actually agree with the Christian story: Don't cheat. Don't murder. Don't steal. But did my CofE primary school ram that into me, did my parents and peers, or did I come to that conclusion myself? I would say mostly my time at primary school and my outside influences in my formative years instilled my morals, but as I got older I realised that it just made sense not to do bad stuff to other people.
Ultimately I do believe life is meaningless, but with caveats. To take a humanist view, I am supposed to do good without God. I'm not going to heaven, because I don't believe it exists. So if I want to make a mark, I have to do it whilst I'm alive. Some people leave behind great art, or music, or written words like plays or TV shows or books. These can be shared with people still alive, and so those people can find value in them. I might work for a charity, or start a charity, and help other people, and the effects of that ripples to even more people, who find the benefits of my work. I might be a scientist, who cures an incurable illness. I might even be a politician, who fights for change in their constituency, to make living in that area easier & more pleasant. So whilst I do my good work, others benefit, but do I benefit? Apart from the sense of "doing the right thing", the accolades and feeling a bit self-satisfied, I don't think so, no. So why do it? Because of that innate feeling, because it's the right thing to do. Justice. Kindness. Altruism. Morality. Being a Good Person. Most of us want to ve remembered in a positive light after we've gone, don't we?