Is your LO teething? It's very normal for babies to lose their appetite when teething. And really it's normal for them to go through phases where they're not as interested in solids.
I wouldn't go back to smooth purees, and I don't think I'd increase milk either as he is getting more than enough. I know all about the fear of NWings, but I don't think that should be a reason to panic and try to get more food into your LO if he is not interested, kwim? We can't force them to eat afterall.
I think it's totally normal for them to start playing with finger foods at this age, and that's ok. He will figure out how to eat some too.
TBH I don't think you are doing anything wrong. Just keep offering, and offer a good variety. I suspect that it's just a phase and he will go back to being more interested at some point.