2) 6AQ5, 6AQ5A, 6AQ5W/6005 that I have gotten are all exactly the same (from the same manufacturer).  It seems to me that the 6AQ5W/6005 are a little less microphonic and a little more uniform in their characteristics; it's probably a selection thing.  I'm trying to decide if they sound better or not.  I think maybe slightly.

3) Bless you, my man.  You know, not one person in four ever flashes on that little detail of the implementation.  I am a forty-year maker of musical instruments, aircraft, sailing yachts, and this stuff.  The umbilical wiring (B+, circuit ground, chassis ground, heaters) runs through the chassis wall.  I will bring one of these to your house, and with a magnifying glass you will not find how I did it.  You have just appeased my (considerable about this stuff) vanity, so if you beg me, maybe I'll tell.

Yer admirer,

Poinz