Beantin DD has been a bit like this on and off the last few days and I've ended up holding her most of the time. I tend to find on days when she is less "windy" she's better. Today for eg after her mid morning milk, she was awful and kept whingeing so I put her in the sling and got on with jobs. Then I gave her some gripe water, she did the most almighty poo and it seemed to shift whatever was a problem. She then just had this angelic look on her face and drifted off to sleep....
I do think that when they are this little, they can get tired quicker than you think. PT your Aaron sounds amazing being content at being awake 4/5 hours - I know with my 2, DS was just like DD - give them an hour and a quarter to an hour and a half and they start going ballistic. I used to leave DS too long before putting him down and he was hard to settle. With DD I put her down the first sign of fussing and she's been so much easier to settle. She always cries a bit - sometimes no more than a few seconds, sometimes up to 5 mins but I know now that she will go - some people feel very uncomfortable leaving a baby to cry at all but you'll know what you feel comfortable with and you'll also start to realise what they want. If DD is mewing a bit like a kitten on and off, she'll go. If she starts squawking and it escalates quickly, she's probably windy and I tend to find if I pick her up, she burps/chunders and then will go down again. Why don't you try putting him down earlier than the 2 hours and see what happens? Also, do you swaddle him? I've found with both my 2, the swaddles have been a great help. DD will fight it but then calms quickly with it. Some babies on this thread have hated the swaddle so it might not be a success for you.
Have you also tried a dummy? I also did this with DS. He wouldn't settle for naps so I used to put him in his lie flat buggy somewhere near with dummy in mouth so I could pop it back in and eventually he'd go off but at least I could get on with jobs without having to hold him all the time.
There is also the sling option. DD will always snooze in the sling...they love it.
It will get easier once he gets a bit more aware. DS definitely turned a corner around 3/4 months. I had a bad week the other week but feel like I'm coming out of the tunnel with DD who is 8 weeks this week....
Sorry , I do go on, but just trying to see if any of these things might help you.
(I never shut up in RL either - have you guessed?!)