Absolutely he won't starve, and it's important to remember that kids don't starve themselves (excepting those with anorexia) and however fussy he is or little he seems to be eating, he is eating enough to keep him going and he will keep eating enough, even if he isn't eating the ideal amount of food. If we know that, then we can feel a bit more okay about it when our kids leave lots of food - which can be really worrying for us, even when we don't need to be worried.
There is nearly always more going on underneath, and food is such a big area of life in many ways, one of the few things they can have control over at such an out of control time in their lives, and as people have said, your emotions, stres levels and environment have quite a big role to play in your sense of hunger/fullness. So it's not surprising that food issues are so common
Not that that makes it easy to live with, I know! But I remember my DS went right off his food a short while after coming to live with me, and both DD's also changed their eating habits. It's difficult, but it all got so much better with time. Food issues are one of the first things to get worse here when the kids are feeling stressed
I'm sure you are doing a fantastic job
I try to take a similar approach to Kew - offering some limited choices, providing healthy snacks they can take at any time without the pressure of being at the dinner table (and I think the family dinner table environment, whilst IMHO the best way to eat, feels quite stressful when you've just moved into a strange house and if the child feels under pressure it can make food issues worse). Basically not making a big deal out of eating. Dinner table is low key and I try (varying degrees of success) to keep the conversation away from the subject of food and don't mention how much the children are eating at all. If the food doesn't get eaten, then fine, it's not eaten. No need for a fuss or consequences, I accept you're not going to eat that and that's absolutely fine, but mummy is not cooking you a second meal of xyz instead. Next mealtime is a new event.
Don't wear yourself out trying to devise new and interesting meals that he will definitely eat all of - if you're serving up a healthy diet and you know he's eaten the food happily before, then you can serve it again even if he says he suddenly won't eat it. Food issues are usually about your emotional state and stress and perhaps about control, not about genuinely suddenly hating abc food forever.
Again, it's early days for your DS and this might be an ongoing thing for a while, but I'm sure you are absolutely doing your best for him always