All of the above...and....
This guy has what sounds like a growing business (the increasing radii of deliveries and frequent requests you mentioned) and he can't finance a truck nor have his current truck repaired adequately.
Perhaps all acceptable used trucks are dear, but he sounds like he wants some glam too. In any event, it's truly not your problem.
The "deliver it tomorrow" angle is also surprising. He might be charging more for this next day service.
Someone mentioned U-Haul.
Let him do that.
It's more involved than merely asking you for your truck and could possibly shift him into "serious mode". Many people need that.
....and while he has the U-Haul, he can use his brain to capitalize on any left-over hours he has before returning it.
FYI: There's a '98 F-150 extended cab 4.6 w/stick TC for sale in Bergenfield, NJ being sold by a reputable towing outfit. It has a plow fitted too!...not too far from the NYS border...if you're near, say, the Cuomo/Tap Bridge.
TRUE STORY:
I had a 1976 F-100 van. My phone rang and a woman who wouldn't tell me how she got my name asked me for my van.
"I don't want you. I just want to borrow the van."
I said no and she made an audible 'haar-uumphy' noise and hung up rudely.
Don't "Jell-O out" on this guy by reverting to your old, generous self. Continue this man child on his road to vehicular self-sufficiency.
"Tuff love"
he’s always out doing something.
Good. Motivate him to do more constructive things without you.
Let him go through his list of other friends. He might actually sharpen his focus and streamline his behavior.