UWB poor you, it's so hard not to get stressed. C is also very fussy (though eats everything he's given at nursery apparently, which I do find takes the pressure off me). I try really hard not to make it an issue because his reflux made feeding so awful in the early days that I can't face food being an issue too. Didn't F suffer with it too?
My tricks include:
Sometimes I just feed C from 'my' plate. He'll eat anything he thinks is destined to go elsewhere!
if I'm worried about his fruit/veg intake I'll give him the Ella's Kitchen smoothies, which he drinks from the pouch and loves.
Baked beans are a good source of iron and also something he will always go for. You can get reduced sugar and salt version.
Fish fingers are a fail safe too.
Often I give him something 'fun' to distract him while I try to get some proper food down too - raisins, baby crisps, rice cakes etc.
I do often offer an alternative if he refuses to eat. This might be a rod for my own back and i don't cook something different but I'll give him a cheese sandwich or something that I know he'll eat (he would survive on bread) and just act as though I was always planning to do that, not that it's a replacement for anything.
i know this all sounds quite slummy mummy but I have taken the view that I'd rather he eat something than nothing.
Also, you could give a vitamin supplement to bolster things.