Food is fun until they're one.

I know it's hard not to worry, but as long as he's still having feeds/bottles, he will be fine.

My DS was very much the same. He even started to lose weight, but then I had to remind myself that he was super active and was still reaching his milestones, having lots of feeds (like 15-20 a day) and lots of wet and pooey nappies. Very very rarely would he eat more than one or two tablespoons of food at any given time. Don't forget our estimate of what they 'should' be eating is often vastly different to their natural intake clock. It's really really important to listen to their cues so as not to disrupt that.

Recently he even went on a self imposed diet of frozen peas only. You can imagine my delight with that phase - NOT.

I have never offered him baby food so I can't really help you there, but he is very much a chewer and a spitter too. Only recently has he begun to ingest lots, and he's nearly 18months old. He only gets offered exactly what we are having, and just like my 4yo he has his preferences and his dislikes.
In order to get as much variety in our diets I try to not offer the same type of meal (whether it be breakfast, lunch or dinner) within a four day period. I found this stopped DS getting bored with what he had and therefore stopping after only two mouthfuls.