This question just keep going round and round the forum

A) I have just bought an external EQ so I can tune the tone to the space - though haven't tried it yet... ...

B) Not a lot, other than try and use a decent sized room and play at, or near gig volume when you tune your sound.  It will inevitably sound duller when you return to practice volumes of course.  You can then tweak to the venue either on the POD, or external EQ (above).

C) This is very difficult without someone flying the desk of your PA.  In truth my preferred method now is X3L direct in to desk, then I use on stage monitors rather than a guitar amp(s).  If there is someone ont he desk, then you can be assured that the audience are hearing something loud enough and they can even cut some highs, etc. if necessary - as long as you trust them of course!!  I have my guitar slightly higher in my monitor mix than front of house, just so it makes it easier to hear what's going on with my playing.

Using guitar amp backline and no PA, it is impossible to know what the audience is hearing, without a friend in the audience pointing at you to turn up/down your volume  - especially once the drummer kicks in

I do find it useful when using an amp to elevate it, or at least angle it up slightly.