For the first question, I would consider whether your son has reflux--that is what I was advised when my daughter did something similar. My pediatrician told me to hold her upright for 5-20 minutes after each feeding. I would pat her back and that would often soothe her. It could also be fast let-down and he is overfull. You might consider contacting either La Leche or a lactation consultant at your nearest hospital to see about the fast let-down of the milk.
I had a similar experience with pacifiers--my daughter has been exclusively breastfed and refuses to take a pacifier or a bottle of any sort or kind. I call it reverse nipple confusion--she just wants the breast and she won't be fooled into taking abything else. She just turned six months old. A lot of the time, she pacifies on my breast. When she was younger she would sometimes suck on my clean fingertip but she now refuses the finger altogether. Like you, I tried many brands and types of pacifiers--I once counted and it was 16. Unfortunately, as a lot of people have told me, some breastfed babies just don't like pacifiers. I understand your concern, however, because you don't want to always be the pacifier (and it doesn't seem to make him happy for you to offer him the nipple), and your son really enjoys sucking. You will read advice that says to help him find his hand, but I'm not sure that's a great alternative either because you can always take away a pacifier when he's older to break the habit, but you cannot take away a hand used for thumbsucking.
That said, my daughter will--on very rare occasions--take a larger size (6 months and up) MAM brand silicone pacifier. It is the one my sister uses with her kids (who were also exclusively breastfed), so they often end up sharing. However, my daughter will only take the larger size.
So overall, my advice is to keep trying with the pacifier (that is what my sister said to me) and if it doesn't work, use the finger, and if you can get away with alternate methods of soothing him, maybe nothing. However, do know that by breastfeeding your son, you are offering him the best possible start in life. Someone said to me that the days are long but the years are short, and it helped me.
Good luck!