1.  No problem there.  That's a good practical way to connect them.

2.  No, biwire from just one set of connectors (A).

I bi-wire my speakers by soldering all of the wires from both runs into a single large Audioquest gold-plated spade lug at the amplifier end.

That gives the best possible single connection. I would stick with using a single pair of amplifier terminals.

On the other hand, I would have no problem with using lugs for the bass wiring and banana plugs for the treble wires.

I figure that the peak current demand is greater on the bass side, and the spade lugs give the very best contact, but the difference should be infinitesimal.

What is more important is using the largest possible wire.

I use four runs of #10 Belden wire to each speaker, but #12 is fine as long as you don't go more than 15 feet.

You might be OK with #14 if your speakers have a sensitivity of 90 db per watt or higher, but larger is always better, and speaker wire is pretty cheap at Monoprice.