Estimating Expenses Before Buying a Truck

I am in the process of trying to figure out an estimate of me expenses if I take the plunge and purchase a truck. I have been driving for 10 years so I am not a new driver but never really considered this before now. I am looking at a truck payment around $1600 per month on a 2008 Kenworth T2000 with a 3 year engine, powertrain and axle warranty. I have done some reading on this forum and other places in dealing with costs but there wasn't a lot of actual figures posted. I should get approx. 6.5 to 7.0 mpg and it has a bunk heater which will help keep that down during winter. I am looking into signing on with Landstar or Fremont. I know how much tags, and IFTA will be but how much should I plan on sitting aside for maintenance and breakdowns, taxes(business and personal), insurance, and accounting? Percentages of weekly check to sit aside would help me figure out my personal earnings and also minimum earnings a week I would need. One person recommended on a website that you take these percentages and set aside:

Truck Payment- 16%
Insurance- 5%
Maintenance-6%
Accounting/Tax Prep-1%
Escrow Account-1%
Tolls/Pallets/etc.-2%
Out of Route Fuel-8%
Fuel-35%
Salary-24%

Do these seem realistic or should they be adjusted. I'm not sure which category tags, ifta, and permits fall into.

 

The 2008 I am looking at has a history of 7mpg on the computer. It has an ISX Cummins 475hp with 3.55 rears and 22.5 tires. I live in PA and my preference is to run midwest, and southeast as much as possible.

 

Landstar wants $1650 got plates and $200 for permits. They said Highway Use Tax was approx. $500. How much should I expect to spend in fuel taxes above what I spend at the pump?

 

I have adjusted my percentages now to this:

Estimating Earnings of $160,000 a year
Figuring a minimum of $1.40 per mile at 114,000 miles per year approx.

Truck Payment- 11% - $17,600
Licenses/Permits/FHUT/Tolls/Scales/etc.-3% - $4,800
Insurances-4% - $6,400
Fuel-47% - $75,200
Maint./Repairs-7% - $11,200
Personal Income-28% - $44,800

Do those look reasonable?