Sorry....meant to add this but posted too quickly....
You can bathe his eyes VERY GENTLY with a mild salt solution using boiled water, and allowed to cool to lukewarm. Use clean cotton wool balls, and discard each one as it is used.
This is just a little symptom relief until he gets to see a vet.
This does sound as if it could be some kind of allergic reaction. Especially as it responded to Benadryl in the first place (but now it has stopped responding.) But of course I cannot diagnose him as I haven't enough knowledge. And no-one can diagnose him over the internet. He will need to be examined by a vet.
How is he otherwise? Is he okay generally? Eating, sleeping, not lethargic? I understand you won't have money until Saturday, but please do take him a.s.a.p. Saturday to be checked out.
In the meantime maybe bathe the affected parts with Witch Hazel diluted with a little water. This should soothe the irritated skin and won't do any harm to him. Please don't put Witch Hazel anywhere near his eyes though!