Hey!
Breathe!! Right if she was sleeping independently before (which she was) you could do WI/WO but you need to bear in mind for a month you have stayed with her until she fell alseep, so UT maybe tough going.
Re; the night light, if she's had one and reponded well, then yes. If she's not, why do you want to introduce it? Do you think it will help?
I would during the BT windown routine, let her know, mummy's going to read you a story and then your going to snuggle down and have a lovely sleep, and mummy's going to go to her room. And then do it .
Re: the hysterics, that can be anger and frustration of your LO as opposed to upset/distress. This is how I've always managed Wi/WO, see what you think:
(1) BT as normal
(2)Get the 'don't go, I need you mummy' patter from R. My response: No R is time for night nights (or whatever your sleepy phrase is), lay her down and leave shutting the door behind me (she sleeps in the dark with the door closed) ... And let the games begin!!
(3)R will kick off the minute I walk away- stand back and assess. Is the cry upset/distress OR temper/frustration. If it's the latter, do not go in. Hold back. There is a difference IMO between upset and angry cries - don't jump in! If it is the former, implement (4)
(4) go in - put back into bed/ lay down and again say sssh, it time for night nights now - and again leave
(5) again stand back and assess and do not rush in. Only go in if you LO is upset not just angry / frustrated. If you need to go back in, say NOTHiNG - simply put back into bed/lay down and leave
(6) rinse and repeat (5) until he gives in - HE WILL. It may take hours the 1st time, it will take less time the 2nd time and so on until he decides it's just not worth the effort
Top tip: make sure you have something to occupy you waiting on the landing - Phone, book, game - something that can distract you and stop you rushing in/ going in prematurely. You will be there for a while so be prepared to stay the course and I promise you will crack it - he will relent before you do.