I would stick with finger foods personally, some of it may be going down and I wouldn't want meals to have negative associations - if your son is fighting you then I would just leave the spoon feeding, at least for a couple of weeks. As long as he is getting enough milk he'll be fine for calories, nutrition and hydration. Formula has vitamins too.
He takes 4/5oz of milk maybe 5 times a day, with water given at 'meals' and overnight. Teething gels haven't helped much at all to be honest, he's more interested in throwing the tube away! He was 6lb2 born and has never taken more than 5oz in any one sitting. I dont want him to feel forced into eating, even encourage him to guide the spoon which gets very messy, but no joy, especially recently.
Well firstly food intake isn't that important at that age, milk should still be the main source of nutrition. My DD was 2nd centile at 6 months (was 3lb13 at birth) wouldn't eat any solid food until 8 mo and now at 14 mo she is a great eater, and is now 25th centile., And I never tried to fight to get food ' in' - I was too worried about causing negative associations with food and spoons.
But have you tried rubbing a teething gel on his gums maybe 10 minutes before feeding time, and/or a teething powder?
My LO is 6 months and has gone right off food since his first 2 teeth came through, the only thing I can get into him is a couple of spoons of banana porrige at breakfast/supper (with a fight) and if I'm lucky a toghurt during the day. He's quite happy to munch on apple slices, toast etc because it hepls his guma but doesn't actually EAT it. We're still on the 9th centile and having plenty of milk during the day but still up every 2 hours on a night for a drink (water) Any advice on how to makesure he's getting enough 'foods' please?