zilla-
I don't know a ton, but 4 crickets for a 4 month old is way under I think. Mine ate as much as I would put in there, every day until he was about 7 months old. Generally 12 to 15 crickets a day. Then he stopped eating for up to a week at a time.
Sometimes appetites go down around sheds. Strange. I'd do fecals at your vet. It's good to get them done once a year anyways. No harm in being too careful, and fecals shouldn't be more then 4o bucks. They should do
a float and
a direct I believe for the first time.
plop-
If I slowly walk up to him in his cage and look at him he runs to the other side... Is this normal?
yup! give him a few weeks, even then, he'll never be totally used to you, he'll tolerate you.
He is also starting to hiss now if i slowly reach in to get him
Oh - it's gonna get worse as he gets older

handling my veiled is literally like handling a venomous snake with legs and no fangs. He fights for his bloody life.
Holding him is ok, but understand he will probably never get used to you/like you/relax, no matter hoe much interaction you have with him. When your veiled is in your hands and stops running or being scared, he might relax slightly, but it's mostly the realization that he's lost all power and he's practically waiting for you to eat him.
This is a generalization - some veiled's ending up being mildly friendly. But I understand that they are freaks of nature!
I'd also recommend you do a fecal in a few weeks if his appetite doesn't pick up. It can't hurt. To be clear both of you should post your cage size/lighting/suppliments/plants/ all that good stuff, just to clear red flags.