i think you are dead on regarding the number of tempos = 2 per week.
as far as the pace goes, i would suggest going by feel mostly as Summer weather can be difficult some days.
you might make one tempo day a faster day and the other a slower but little longer one.
1) 4-5 miles = pushing it a little
2) 6-10 = cruising
don't worry so much about the time/pace but instead listen to the feel of the run - your breathing, etc. If your mind is getting frustrated trying to run a certain pace, you are going to fast. Don't try to run the whole distance at the same pace = allow you body to build into the run...the early miles should be a little slower (especially the first mile)...i wouldn't even bother timing it.
don't worry about the pace on the other days either - these can be fairly slow at times = when the body is tired. 8:00-9:00 pace is not too slow. There are even hidden benefits to going slow occasionally. Gradually increase the overall mileage...and be sure to take a day off every so often when you just feel you need it (about once every 7-10 days for sure). If doing this bothers you because it lowers you overall weekly mileage, you are becoming too obsessed with the weekly totals. The goal isn't total number of miles, but slowing increasing the workload your body can handle. Super Compensation To get effects, you have to rest and have slow days.