Let him get the Model 3. Last time I did the math (granted, for my LEAF), the cost to refuel was roughly equivalent to driving a (50 mpg) Prius when gas was $2.50/gallon. That was on LADWP, I know SoCal Edison (which I think you're on?) is even more expensive for electricity. Tl;dr don't expect huge fuel savings because our electricity is so fucking expensive. It's not nothing though.
The leases kinda suck, but the good news is that Teslas have really high resale value compared to other cars. The maintenance savings are real though, literally the only thing I've paid for on my LEAF in 4 years/35k miles is tires/tire rotations.
Because you'll have another gas vehicle anyway and California's supercharger network is so built out, there's no good reason to get a larger battery. The standard range+ has a 240 mile EPA range and "partial premium" interior starting at $39,900 (before $3750 federal and $2500 state rebates), feels like the sweet spot. Otherwise you're spending 10k more for an extra 70 miles of range and a few interior perks (premium audio, rear heated seats...in California, and a whopping 1 year of satellite maps/traffic info and internet browsing) - not worth it.
Let him buy a standard range+. And don't pay for full self driving, let other people be Elon's crash test dummies for the next half-decade plus it's fucking $6,000 and who knows when it'll actually be released. Autopilot is standard anyway for highway cruising. If he wants to be fancy let him spring for a different paint color and/or the 19" wheels (that look way nicer). Make sure you take delivery before July 1st (or you'll lose another $1875 in federal rebates). Do some internet shopping for your car loan, you should be able to get a much better APR than Tesla is offering.