You do sound overwhelmed. The good news is that with small children 'phases' pass in time. From what you say, I am concerned that your son's discipline problem is not confined to the bedtime issue. Is Early Intervention involved at all? Your two year old would benefit from speech therapy and your son may have undiagnosed problems for which you can get help.
It is important for most children to have very strict routines to help them learn what is expected of them. If you don't already have a special and fun bedtime routine, then start one to include a relaxing bath (lavender essence will help relax him),snacktime and storytime. To wean your son away from you lying down with him, set a timer for 5 minutes, then let him know firmly that it's time for him to sleep and you will see him in the morning. If he does awaken during the night, bring him back to his room with a gentle but firm reminder that Mommy needs her sleep and that he is required to stay in his own bed. If he cannot stay in his own bed like a big boy, tell him you can get the crib back out and put one of those zipper-locked tents on top to make sure he stays there. His temper tantrums may be hard to take at night, but giving in only makes it worse.
Proper diet plays a big role in how children behave as well. Be sure you eliminate sugar, refined carbohydrates, artificial flavors and dyes from their diet. In other words, if it's not 100% natural (certified organic is best) then don't feed it to your children. I have seen many cases of ADD and ADHD, as well other behavior problems treated succesfully with diet alone.
Having raised three sons as a single mom (my husband passed away then my youngest was 9 months), my heart goes out to you. I urge you to see help from Early Intervention and any other agency in your area that provides support for young children and their families.