ok, lots of questions... let me try and give my answers in a rational way... wish me luck
first off, i have no experience with small HID's... but from what i have seen you will have plenty of room for 150 watts in there without moving the top shelf... i think
the single HID wont take up as much room as all the CFL's. it will only come down from that top shelf a couple few inches. also, using a ScrOG setup for that cab will give you back a few inches.
how to tell how far the bulb should be? the common wisdom says put your hand on top of the canopy and see how hot it is. if it is too hot for you, it is too hot for your plants and needs to go higher. if you can hold your hand there and have it not feel cooked, it is ok.
i couldnt imagine ScrOGging without topping (i actually prefer fimming) or LST training beforehand... but i am still new to this ScrOG thing myself
my buds were all kept within 4 inches of the screen... the main colas (yes, plural, love that topping!) were over 12 inches long though and ran along the sides of the screen... it turned them into a bunch of smaller buds standing up from that main branch.
the thing with any sort of plant training is the goal is YOU keep the plant where YOU want it to be... fuck what it wants to do

twist ties and razors put the game in your control.
basically, the growth you have above your screen is higher than the growth i had over my screen at harvest. and you have WAY more leaf growth than i do! you stem diameter also seems about half what mine was.... and your screen itself is 2-3 times as far away from my soil... i think... pics are hard to tell. i am NOT saying do it my way, i am just giving you data to compare and come up with your own plot.
ventilation... do you have your exhaust fan blowing into the exhaust or sucking from it? regular PC fans sometimes do poorly with a tube behind them that they have to pull through... they spin but dont really move air... so you may want to have it push through the exhaust or go with a larger (CFM, not inches) fan.... mine pulls through my exhaust, but the fan is not mounted to the tube, it is mounted to my light baffle. play with how you have the fan mounted and see what happens... a good way to visually see what a fan is doing is with smoke.... sit in front of the cab, do some bongs and watch where the smoke goes
as for your clone... looks like you shocked her... just did the same thing last week to one of mine... she laid down for like 2 days and i thought for sure she was a gonner... even one of the leaves totally dried up. but i wanted to see what would happen so i kept treating her like the other three clones and she stood back up and looks good now
which brings us to: always take at least 2 clones at a time. you can always cull if they all survive but you will lose days/weeks if you have an accident.
push that soil TIGHT around the stem! that is what kills most clones i think... if the soil doesnt touch the stem the plant cant get any water and dies.
and finally, do NOT over water your clones! i give mine a small shot of water twice a day, just enough to keep the jiffy they are each in moist. wet leads to rot which is death.
if you keep that clone moist and dont cook it with the lights and keep the soil against the stem i would almost bet it will pull through.
the almost comes from you are trying to clone at the hardest time... cloning from flower is skating uphill. takes longer for them to take root. that means rot is more likely to set in. no worries though, cloning still works from flower, it is just harder and more prone to failure.
ok, i think i spouted off my opinion and POV on your last questions... miss any?