fuzzy what you just put is completely normal to me. i have lots of memories of them being sick hours after feeding, obviously there will be exceptions and it could be something else. ( i always seem to put that! its cos in the back of my mind, im thinking what if i say its normal and then it turns into something serious) 
i think being on here can be a double edged sword scheh it helps enormously at times but it also highlights any differences between the babies and has you thinking- shit! my babies older/same age and they're no where near doing that. i really think you should cut yourself some slack sweet. you are doing a fab job. he is clean, fed, smiling on pictures on fb, wearing nice clean clothes (count mine up and see how many sleepsuits eva is in
) and i seem to recall he is sat up unaided on one. the little buggers do everything in their own time.
i dont really have a circuit thing going on. she sits in her bouncy chair for ages, watching twins playing and sometimes the tv. if she cries and i want her to go a bit longer i will put the bar with the dangly thing over it, or pass her one of the lamzee things. if she still doesnt stop i know its hunger or attention so i just pick her up and hold her or feed her. i once timed how long she went for just sat in the bouncy chair and it was an hr and 10mins before she whinged. i honestly forget she is there.
i see people with dangly toys hanging off car seats, prams etc and i just think they are playing their hand to soon. mine have nothing. i dont give them anything when we travel in the car either and they just sit there looking out the window. went shopping to a different supermarket the other day and its at least a 20min drive there and back and they didnt peep once.
if they do start whinging, i usually give them a drink,. and then leave it, when if they start whinging again, a banana etc. then wait and if its a particulary long time in car or pram a book. if you start off giving them a toy/ book and they play with it for 10mins and then get bored- where do you go from then? they need to learn to be contented without constant stimulation i think- for MY sake!!!!
speaking of comparisons though, i had eva weighed today and she iz 16lbs 7oz. she was 16lbs 4oz during the feb hols about 2/3 weeks ago. i knew there was a reason why i never weigh them. im all simmering worry now, as i dont think thats a lot of weight gain at all! 
repeats mantra style argh