Right, President's Circle should get you some nice upgrades at SLC. With all the renting you'll be doing, you should qualify for PC through the end of 2019, so if you lose your UA 1K you should be good.

Accruing Hertz points for personal rentals is a good use of the credit. You could also credit to United and get bonus points. See here for more information. Honestly, AutoSlash can get you much better rates than what you'd get on this page, but if you are expensing it to your client, you may not be very price sensitive.