Hi Sonnylax-
Congrats on the Leaf Lease. I think you'll be pleasantly surprised to learn you should get the full $5,000 tax credit. The credit of 20% of purchase price up to $5K is based, for leases, on the capitalized cost. So as long as the capitalized cost is at least $25K, you get the full $5,000. It's not, as I thought once too, based on what you actually pay out of pocket for the Leaf.
I can attest to this as I've already received by $5,000 for the Leaf I leased last November.
Although you have to file by paper for the EV credit, I received mine in about 4 - 6 weeks. Much faster than those who submitted in 2011 and had to wait about six MONTHS from what I hear.
As for the tax liability statement, that just means that you have to pay at least $5,000 in taxes to get the full $5,000. If you only paid $4K in taxes, then you'd only get $4k for the credit. I think you already figured out that it's your tax liability and not your actual refund.
As for the charger credit, I don't have the details in front of me, but I recall it was only for COMMERCIAL chargers. I don't think GA gives you a credit for one you install in your home (but I might be wrong).