First of all, hang in there. I know it's tough and can completely understand. My son was a pretty horrible sleeper the first 9 months.
My first thoughts are this: have you check out the 4 month old sleep post and 4 month old schedule on Nicole's blog? If not, you can find them here: 4 month old sleep, 4 month old shcedule. Compare how your current schedule is different or similar to the one Nicole recommends and then see if you can make any adjustments that might help.
It could be that the time you go to bed happens to coincide with one of his light sleep cycles. Have you tried using a white noise machine or some other white noise like an ocean waves CD playing at night so he doesn't "hear" you come to bed so much? This might also help with how his noises keep you awake. My son was a noisy sleeper too and I know exactly what you mean about being kept away or on edge that the noises mean he's waking.
I would also say picking him up and bringing him to bed each time he does that first wake up might led to a sleep association problem later on. It's best if you can work on feeding him, if need be, and working on getting him resettled in his own bed.
What is your current nap routine during the weekdays? Do you have a nap routine and have you tried darkening the room he naps in? Some kids are really sensitve to daytime light during naps.
I would also recommended downloading Nicole's 7 Common Napping Mistakes and see if there are any tips in there that might help. You find it HERE.
Please post back and we will continue to troubleshoot and hopefully get you on the road to better sleeping and napping.