Of he starts spitting I think stopping would be great. Then try again later if he seems interested.

Not a big deal as long as he is still getting breast milk/formula on demand since that's where he should be getting the majority of his nutrition. 'food before one, just for fun'.

Maybe he's ready for new textures? The next stage of foods? Have you tried finger foods? My lo wouldn't eat purées so we ended up BLW (he's got a bit of a stubborn independent streak!).

I would just take him out of his high chair and try feeding him again later. Maybe he just doesn't want to eat.

Should I keep feeding him once the spitting begins? Not that I am going to starve him... but he doesn't swallow anything, he just spits it all out!

Just a phase it'll pass, in the mean time buy a pressure washer, lol! Sorry it's rough, I remember with my other two just saying no and frowning. I don't know if that really helped but they eventually stop.