Hey Hon,
Just chipping in with been there done that and still doing it

. DS is 20 months and we are at the 4th phase of the same thing. I have stressed myself to the hilt over this problem. I have been a conveyor belt of offerings and picked up more food of the floor than the average family dog

. I have also researched fully and have found that the following is the best way:
Offer things that you know he likes. He is becoming more independant and it's perfectly natural for him to want to do it all himself now. Along with his favourites offer new things, incuding vegetables at every meal (even the ones you hate

) When/If he's finished the things he likes try and avoid giving him more in order to give him the best chance of trying another thing. DS has just eaten broccoli this week at roughly the 13th offering

. If it goes on the floor don't immediately pick it up and give it back, it just adds fuel to the fire, but when you get him down from the chair encourage him to help you pick it up with you, even if he just does a little bit, it helps him to understand the consequences of mess making. Buy him some new exciting plates and cutlery, this worked for us, DS loves his spoon with the penguin on it

. Nutritionalist and paediatricians say 'It's not our job to make children eat, just to present them with a variety of good and healthy food' Also as PP said bear in mind there are spells of growth when LO's will eat more. We have just been through 5 weeks of what you're suffering and just yesterday DS started to eat like a horse

I suspect a growing spell. Never ever force feed (sorry I know that's DH idea) it will enforce all kinds of future anxiety and problems. It sounds like DS is picking up on the stressfull atmosphere in your house Hon with you saying he ate at Nana's, maybe he felt more relaxed

Sometimes if you box clever and put his food on a plate for you and sit next to him he will want it because it's yours (in times of desperation on your part LOL) Don't make mealtimes too long, generally if he hasn't eaten it in 20 minutes it aint gonna happen. Try and cut down on filling snacks if he has 3 set meal times but if he doesn't eat much at lunch time (this is common) then allow him to graze in the middle of the day, that's one less stressfull mealtime for you. Oh and one more thing, when you give him his food leave him to it. I have found being spectated is the number one way to make DS eat zilch!!! Of course if you're all at the family table eating together that doesn't apply.
Hope some of this helps Hon. Chin up.x.