L.S.
Not in your shoes, but I can empathize. I can only imagine how your heart breaks when you leave him and miss out on things, but try to focus on what you are doing for him. You're busting your butt to give your son the best life possible. And while he's too young to get it now, one day he'll look back on all you sacrificed for him, all you gave him and will appreciate it. Know that you're doing the best for him, even though it's emotionally difficult for you.
As for strengthening your bond? Just spend all the time you can loving him and being there for him. Snuggle and read before bed. Start a weekend tradition of cooking a special breakfast or something (and ask your mom not to make/do that *particular thing.
Trust that you're doing the best for him.....and no one will ever love him as much as you :)