Good grief, don't execute the poor guy for having a load on the back of his brand new pickemup truck.
Yes you're over pretty much every paper limit by a little. You're probably also right there or a little over on tires.
Realistically, you have an adequate vehicle for towing your trailer. Wouldn't want to go any bigger with your particular truck and I'd at least look into getting some tires that are heavier duty.
Tons of options for 18x8 rims. From your P rated tires, there are like "super Ps" called XL. Typically 50 psi max and a bit better weight rating. Or load D or E LT tires.
If $ is a factor, you could buy a set of new LT takeoffs on Craigslist. Tons of them for sale coming off 3/4&1 ton pickups in favor of bigger gnarlier tires. Get a whole set for like $600 or less pretty much new. Then sell yours. You could upgrade for only a few hundred bucks.
That said, I've tried to kill P tires on half ton pickups many times. They are tougher than their rating. Pump them up and go.
Happy campin!