Grease monkey, I hate to say it, but ALL of these things you ask should have been asked BEFORE you bought the truck.
You will need to add up ALL of your costs, EVERYTHING, ins,truck payment,license plates, and come up with a per mile figure, and don't forget to pay your self at least 35 cents per mile (thats what a company driver makes)
My cost per mile is 60 cents, that is WITHOUT fuel or my pay, my truck is paid for, but there are heavy repairs since it has a million miles on it.
Cheap tires are $300 a piece, as far as other repairs, there is no way to tell what will break next.
Clutch figure on $1500 in a shop
Trans $2000 over the counter
Front rear $2000 over the counter
Oil change, $125 doing it your self
Brakes $100 a wheel doing it your self, add $100 a wheel for labor
Radiator $1000 over the counter, I just put one in.
Engine over haul, starts at $7000 and goes up to 20K
Starter $200 over the counter
Most truck shops charge anywhere from $75 to $125 an hour.
Cracks me up the grocery store doubles the prices over the last year and blames it on transportation costs, but the freight rates are down, It's nuts.
A 50 cent a mile raise for trucks would come out to less than 1 cent a pound for a steak, no one would even notice it.
As far as going direct with a shipper, you will find that almost impossible, most shippers will NOT deal with a one truck operation, they want a load moved NOW, now when you can get to it, thats why the deal with brokers.
If you know someone where you live, MAYBE you can get a few loads.