If you are having a hard time controlling your anger, I urge you to PLEASE get help. Even if you don't physically damage them (I hate spanking, but I know what you mean - what else can you do with timeouts (including for myself) and other punishments. Please talk to your doctor. Having kids clicked some switches on me and now, after finally getting real help (although I'd seriously tried before), I am realizing (and being told) that no wonder I was depressed and overwhelmed. I won't go into all my challenges, but they're there. This person can also give you coping skills, which will help be a good role model.
Your 3 year old is probably outgrowing naps. We need it more than they do! I'd consider dropping them (except when ill) and putting in an earlier bedtime. That has really worked well for us. What is wrong with napping with him? I've always done it with my kids - an ahhhhhhh moment. On the finger sucking, he could be suffering with anxiety - the closeness of naptime and bedtime (more later) can help with that, along with you getting help (meds or no meds, but therapy can help and can be affordable with insurance) to avoid yelling or overreacting. I didn't know I was overreacting - it was all I knew! My therapist has put me on meds because mine is biological, but she shows me coping methods, too, which has helped. Plus, she's validated my feelings so I don't feel so wrong all the time!
Bedtime: Ours is pretty good, and I did this from the beginning. I lay with them to read the books as they lay on my shoulder. When young (as my little girl is), I then turn the light down and have them turn over. I rub their back (sometimes they fall asleep, either on my shoulder or they turn over) until they go to sleep. Then I leave. At this age, I'd still expect a nighttime visit, where you can carry him back to bed and lay with him for awhile.
My son is 8 now and after book reading, which at this age I do sitting at the foot of his bed, I can leave and he's in bed all night. As he got used to me walking him back to his room and laying with him, I started leaving after he went to sleep again (sometimes I did, too). Then, I slowly changed so that I left as he was near sleep, kissing him gently. Then I was able to leave right after I returned him to bed, usually with a bribery that if he stayed there he'd get a reward the next day.
What I didn't know at the time is that he actually was ADHD, which can keep him awake. I now give chocolate with melatonin in it to the kids, with the Dr. approval. I get mine directly from a place called Dreamerz and give each a half of a choc. bar. It helps.
Try a reward, rather than a punishment system and soft, mild music at bedtime during prep time. Putting a positive on bedtime will help all of you, over time, get more sleep.
Good luck to you. Wish it hadn't taken me this long to finally get validation and true help. My parents yelled, punished and belittled all the time and it's left scars, plus not knowing otherwise. I swore I wouldn't be like that, which, besides the fact I felt horrible all the time, pushed me to push for help.