http://www.acbl.org/...aSingleton.html - this quotes the (ACBL, GCC) interpretation of the regulation clearly and concisely.
http://www.bridgehan...ALANCED%20HANDS gives a more technical answer. Note that both of these articles are old, and the GCC has changed under them, but that doesn't change the argument.
In particular, we need to see that there is a systemic call for some 15-17 handshape without a singleton that isn't 1NT, therefore your system does not force you to "judge" to open it 1NT. If that is not the case, then you're not offloading "rare" unbalanced hands "that are not strictly showing point count"; it's not Natural, so unless you're playing it 15+ and forcing, you're playing something illegal under the GCC.
Also see the requirement to not have a systemic or implicit way of not landing in an N/1 fit if partner decides to put you there opposite a more balanced pattern. Open the hand in Flader's article, and you'd better be a good little soldier and accept the transfer to spades - and certainly can't be playing "anti-superaccepts" to get out in 3
♣ (or 2
♥) with a hand like your 2).
In answer to the original questions, it's clear that 1NT is intended to be a catchall, NF, "15-17". That agreement is not GCC legal. In fact, all three of these hands look like reversers to me (and if it promises 18, so be it. Let's hope we're not in a total misfit). And in the club, the club Director or owner is entitled to allow or bar pretty much anything they wish (although almost all will be effectively GCC); I've played in clubs that wouldn't allow a strong club system on a night (but would allow a weak NT in a natural system), and clubs that technically didn't allow strong pass systems, but if nobody complained, and you were willing to play something "normal" against the odd pair that asked you to, well, that sort of thing got overlooked. Something close to both of those happened *at the same club* (on different nights, obviously).
Answering the OP question at #9, yes, it is a judgement matter. A/K=4=4=4, and in particular, 4=4=(4-A/K), "everybody" would consider balanced. Make the K in Flader's example a 2 and fewer would. Make it 5-4, in particular 5-4 Majors, and fewer yet. Nobody in their right mind would consider that 1=4=1=7 albatross "balanced".
Were you to be allowed to play it in a particular game, an Alert (rather than a range Announcement) would be required, and if it were to be done in a "non-GCC treatments must be Pre-Alerted" environment, then yes, Pre-Alerted.
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)