If the inscissors are broken it should be obvious.As the piggy can eat once the food is in the mouth,it does sound like broken inscissors.These will grow back very quickly,in a few days or so.There is nothing a vet can do for broken inscissors but it would be as well to get the teeth checked to make sure the molars are o.k.
You will have to syringe feed even if Thomas is trying to resist.Guinea pigs are grazers so the digestive system will break down after only a few hours without adequate food.
If he does not like the mashed dry pellets,try liquidised veggies.The small jars of pureed baby foods are very good,the potato and carrot one is the favourite.You could put a bit of the dry mix mush in with this to flavour it.Make the mixture to the consistency of thick soup.Mashed banana is liked by some pigs as well.
While he is off the food,give a vitimin supplement daily.I use Abidec ,one drop per day.
Give plenty of water by syringe as well.
There is no need to get up in the night.Give a good feed as late in the eveining as you can,and then when you get up in the morning.
If Thomas is fidgiting when you are trying to feed,wrap him in a towel firmly so he cannot knock the syringe out of your hands.
Do let us know where you are because someone will be able to point you to a good vet.It is important to find a vet who is good with piggies because some vets will not do dental work without aneasthetic.....