Hey Tom,
It's impossible, or at least very difficult, to make an
accurate diagnosis of someone on a website and based on minimal information, in my opinion at least. The best you'll get is an (un)educated guess, so here's my uneducated two cents worth....

striking collection of sensations at the crown, then 3rd eye,
What sort of sensations? This could indicate a lot of stuff and it's not a lot to go on.
at throat a very strong energetic pulse which forced my head waaayy back for some minutes
Possibly kriyas, it's to do with kundalini which, if this is the case, would suggest that you have indeed crossed the A&P at some point in the past.
strobing of breath at nostrils in tact of breath
Hmmm, could be anything from 3rd to 11th ñana as strobing is seeing impermanance. What happens here?
much facial muscle twitching / pulling
Again possibly kriya-related, but also likely to be something to do with 8th ñana. Knowledge of Disgust. I say this because facial contortion is something which happens here in my own practice.
You'll move through the jhanas anyway while doing vipassana, but absorption is a different matter and not essential for insight which, I'm assuming, is primarily what you're aiming for.
What do you expect 1st jhana to feel like? Look for tingling, pleasant sensations on your skin and stay with that.
The level of experience you're describing from your previous practice would indicate to me that you're more than likely getting into the jhanas without much difficulty, but you might be looking for the wrong signs to show that you're already there.
With the A&P, it's not always a massive deal but it's always the point of no return. It may have been the point where you decided to first get into meditation, it may have occurred years before but it doesn't really matter 'cause, when it comes down to it in the here and now, it's gone and there's no point scouring your memories for it. Focus on being here, now and with sensation as it arises and passes, and you'll see soon enough what we're actually talking about here. Once you can identify it in practice at present you're more likely to think "Oh yeah! Now I remember, I had feeling when I was waiting for a bus..." or whatever. It's universal but it can manifest in a lot of different ways so don't get too hung up on textbook definitions, MCTB is an amazing, wonderful and, for me, life changing book but I did the same as you're doing and set up these expectations which, in reality, may not be exactly what happens for you.
One thing I just need to pull you up on here.....

despite having no concious memory of having an A&P in this life
Forget having crossed the A&P in a past-life, whatever your belief or interpretation of rebirth is, this is not the way it happens. That sort of thinking isn't helpful and I would advise against it, focus on what's happening right now 'cause this is the only moment that matters. If I were to believe the past-life "memories" which have appeared for me, I've been an African shaman and a Spanish soldier, amongst other things, but none of this is helpful or shows things as they are. Take this stuff with a pinch of salt and stick to sensation 'cause that's quite literally where it's at.
Good luck and I hope this was of some use to you.
- Tommy