There is very little cell phone coverage anywhere in rural Nevada. If that's a major concern, then the only way to cross NV is on I-80. Along US-50 between I-70 and Fallon, your only fuel/food options are in Delta UT, Ely, Eureka, and Austin NV (and it's very limited and gas is expensive in Eureka and Austin). Stock up on everything in Ely.
On I-70, there is no food/fuel between Green River and Salina UT, and very intermittent cell coverage.
Tioga Pass into Yosemite is generally open well into October.
Rachel is it along the ET Highway, there's nothing else. There is no gas between Alamo on US-93 and Tonopah on US-6.
The only way to comfortably get from LV to SF in 1 day is via Bakersfield.
Now - you have 4 days and you want a diversion. 2 long days will get you to LV, then you could take 2 days going via the ET and Yosemite via US-93/NV-375/US-6/CA-120. Where to spend the night would depend on what time you got to Lee Vining, that's the last lodging before you enter the park. The only affordable lodging inside Yosemite are the tent cabins in Curry Village, and west of the park you have some choices. It's only about 4 to 5 hours to Sunnyvale from Yosemite.
However, if you are moving to Sunnyvale, you will have plenty of opportunities to take trips to Yosemite on your days off.
Going via the northern route is feasible in 4 days, with your overnights in Raton/Trinidad, Grand Junction, and Ely. An option instead of going via Denver would be US-50 from Pueblo to Grand Junction. It won't save time but it's over 50 miles shorter and it's very scenic.