Here's the link to the division of responsibility model chat thread
The Division Of Responsibility trust model for selective eating child I actually haven't read any of the books but when I read the thread at the beginning of it, it was very close to how I'd always approached meal times with DS anyway.
I also wouldn't say no TV as a consequence of not eating, nor would I give treats, bribes or rewards for eating.
In the situation you describe I can see how you needed/wanted him to not become grouchy during your meeting and so gave him food when he had previously had the opportunity to eat and not taken it. Generally though I'd be of the attitude "I gave you breakfast, you didn't eat it, now there is no food until snack/lunch" (whenever the next routine meal is available). At certain times, when possible, I'd probably also package up the left food and that's what would be given for the next meal. I never force my child to eat food he doesn't like but I also won't go down the route of unnecessary waste either.
I would continue with your new routine of sitting down (no TV) at the table to eat. Sounds like he's kicking back at the new routine but you've already been through several tantrums of frustration so it would be a 'waste' of working through that if you backed down now. You can’t force him to eat and swallow, but you can keep the 'rules' of food at certain times and for a limited time (ie it is not available all day, 20 mins for a meal and then it's gone and no food until the next scheduled meal).
WRT weight, you are offering food 5 times per day, this child is not going to starve. Cast a mind to children in certain parts of our world where only 1 or possibly 2 meals per day are even available and release yourself from the guilt you are feeling about this. It's your job to provide meals, it's his job to eat them xx