Bob, if you have the buying power you reference you should not be wasting you time here. If I were to do a job that the customer buys the material it better be what i spec'd. If not the work stops until the right supplies are on site. Sounds like a cheapie to me.
Your first problem is getting design and engineering help from a counter man at the supply house. I have been in the trade for 45 years and I know quite a few counter guys. They sell the product however they have probably never installed it. Let alone getting it to pass inspection. I see no...
You say the wiring was a bit different. Did you connect the wiring the way it was or by the schematic on the ballast. Also did you install the correct lamps to match what the ballast called for?
Don't know what your local codes are but everywhere I have worked requires a approved means of support. Also since it is outside in a wet area the conduit must not be right up to the brick. A minerlac conduit hanger is what I would use. It will allow the compression couplings to be tightened and...
Just ballparking this I come up with around 3K. One thing that drives up the cost is the ceiling height. Another thing is everything would be out of garage. I would not do the job unless it was. Add another 1K to climb over junk.
I see 2 easy solutions to your problem. 1 is to run conduit from the existing panel to the new sub and use thwn wire. The other is to use type UF cable.