Please help with battery/memory drain

My phone (LG3 Vigor) is completely unreliable because of the memory and battery drain from Google Play Services. Two or three days a week, in just a few hours, with the phone idle and unused, the battery drains completely.

Google Play Services regularly is using about 35% of the battery. At least once a week (often more), it eats up about 1 GB of memory; I have to clear the data.

Here's what I've tried so far since the problem started:
-I took my phone (LG 3 Vigor) to the Sprint store and the technician did a factory reset (because he didn't know what else to do).
-I have very few apps on the phone.
-I added an SD card and have my photos and a few apps on that.
-I've turned off auto-sync and automatic updates.
-My location services are set for battery saving.
-I have the Doze app to keep apps from contacting the network while the phone is idle.
-I frequently turn off the phone and also do soft resets by taking out the battery.
-I also tried the GS Service Fix app that I read about on one of the forums.

I've seen instructions to uninstall updates on Google Play Services and then reinstall them, but that option is not accessible for me (it's grayed out). I also cannot disable Google Play Services. I think I have the most updated version of Google Play Services.

I'd welcome any suggestions that are feasible for someone who has little technological ability! Thanks!

One more point: Some days, it can hold a charge perfectly fine--like, it won't drop below 85% or 90% after 15 hours (I don't use the phone a lot). Other days, even with no use, the battery is gone in a few hours.