I don't think he sounds like he is ready yet. As others have said, you are aiming for 6 months if at all possible. It's impossible for us to know whether their guts are ready for solid food, because we can't see inside, but research shows that all babies are definitely ready by 6 months, so it's safest to wait until then.
The fact he is advanced in other ways is great, but it's not really relevant, because their development often advances at different speeds. For example some babies walk before they talk, and others talk before they walk.
The signs that are said to show babies are "ready" for weaning are really just guesswork. In my opinion the ones which are related to the BLW approach make the most logical sense, but we can't know this for certain. If you decide to wean before 6 months I'd always go with a BLW approach, so that the baby can control what they are taking in and (in theory) this exterior development relates to how developed their guts are internally. You can also do "the banana test" where you put a chunk of banana on their highchair tray, and then watch - don't help at all, just see if they pick it up for themselves and manage to eat a bit of it. If you are going to do this they need to be very strong at sitting and not slumping over or reclined at all (this is a choking risk.) It's very unlikely a 4 month old would be able to pass the banana test, but some 5 month olds do.
Watching you eat is normal at this age - they are fascinated by adults and want to see what we are doing! It was when it became a mammoth task to stop DS from crawling up to the table and just taking the food off my plate that I thought, hmm, perhaps he is ready now!