Battery level for long term parking

[N2STY]

I would have car charge at 80% and use a battery optimizer or if you don't mind resetting stuff disconnect the 12v just the negative

 

[Alb]

I think 50% is considered the optimum but it isn't that critical. Best to avoid both a high and low level of charge.
The 12V battery should be OK for this period but it won't hurt to use a conditioner.