How do you reassure yourself when your toddler refuses to eat?

I am someone who functions off of evidence. If I can find factual information that I can repeat to myself when I'm having anxiety around his refusal to eat then I can get through the urge to make 100 meals or try to force feed him which I am ashamed to say I've done a few times. I will also admit that he has always been 85-99th percentile for height/weight so I am feeling really stupid about feeling this anxious, but I think it's because he's starting daycare soon & this will be out of my control even more.

TLDR is it actually true that as long as the toddler is growing at their pediatrician visits then it's fine for them to be eating basically nothing or just living off of berries, water, and some cow's milk?

I am really struggling with the change in my 16mo eating habits. He was suchhh a good eater as a baby, now it is PAINFUL for me to see him refusing to eat so often and I am spending so much time, energy, effort, etc around planning & making him multiple options to eat every meal. I work from home part time & my nanny will offer him whatever as well just to have him eat something. Whether it's molars coming in, new virus of the month, or just general pickiness, over the past few months he is suddenly not wanting his old favorites, or sometimes he will just flat out refuse what I've made. I WISH he was a chicken nugget kid because at least then he'd be eating chicken, but nope he basically only wants fruit all the time. Lately he's not even eating his veggie pouches which I didn't love giving to him as much as I was but at least he was eating vegetables!

To top it off, he will be starting daycare for the first time in a couple months when he turns 18mo and I am so nervous about what to pack him for lunch. I am worried he won't eat and then I won't be there to give him an alternative. There is an option to buy lunch that is delivered hot by a local grocery store and I'm not sure if I should do that. They don't have a microwave at his school. I am especially nervous that he will be given all of his food at once, so he will probably only want to eat the fruit & nothing else, meanwhile at home I give him the main meal to start, and offer the berries afterwards.

Everyone that has their kids in daycare says "they will eat, mostly due to social pressure & copying the other kids" and whenever I've asked the pediatrician she says "as long as he's staying hydrated" but this is difficult for my brain to understand because we need more than water to survive no?!

Do I really have to wait until his 18mo appointment when he's about to start daycare to find out if he's still growing or not? Is that really the only metric the pediatricians care about? As long as he's growing on his growth curve it really doesn't matter what or how much he's eating?? This is very confusing to me, to not care about nutrients as long as he's growing? But then I remember that so many toddlers are this same way & they must all be growing still?? I just hate to ignore this until/if it becomes an issue. Please help bring me down to earth I need a reality check from parents of older toddlers & probably this is because I'm a first time parent he is our only child. I also want to clarify I am aware there are toddlers with actual feeding issues or difficulty gaining weight or growing & I have no reason to think I am going to get there, but maybe my anxious thought is a "what if" to maybe me getting there eventually??

Signed, Anxious personal chef mom to picky toddler boss baby