I am sorry to hear about your loss.
I'm impressed with what you are going to do.
But do you already have your plane ticket?

Memphis is hot, but it's way different than central Nevada in July.
Also, the WX has you climbing 10,000 feet by Day 3.

You may find it far more pleasant to ride the TransAm -
Leaving the Pacific coast from Florence, Oregon.
Cooler temperatures, less climbing, more services, more riders.
If you already have your ticket, you could always take Amtrak overnight to Eugene.

Please understand that the Central Valley and parts of Nevada have already been well over 100.
Also, that distances between ANY services along US 50 are 70 to 80 miles.
There is precious little shade - on top of passes - at a few rest stops.
(For ex. - the rest stop between Austin and Eureka has picnic awnings, but no water on site.)

Nevada is doable in July, but requires caution and, preferably, experience.
The reason I mention Oregon is - - why be miserable?
Many people bag a trip when they have day after brutal day.
(Not to mention heat exhaustion or rashes in unmentionable places.)

I commend you for this effort - and wish you much success.

John

PS - Yeah, you can hit Memphis and then ride across Tenn & NC to the coast.