Welcome back to the hobby!!!!

Here are the answers for you.

1. You can still use the ESV to check your batteries. This is what I use to check my batteries before every flight. It's probably one of the better practices you can have.

2 & 3. In your case you might want to consider something like the Great Planes Triton 2 charger. It can charge Ni-Cad, Ni-Mh, Li-ion, Li-pol, and lead acid batteries. You can take it to the field and quick charge your batteries at the field if you need to extend you flying day.

A quick note, with the larger size of battery packs these days you may find that you don't need to field charge. A 2000+ Mah battery pack can easily handle a full day's flying without needing recharged.

Hope this helps

Ken