3.6 is not great, but it's not terrible! I'm guessing your age is probably a factor as well?
The PAPP-A (which I am guessing you meant by protein) being normal is great!
Did they see the nasal bone do you know? That can really mess up statistics.
The high bHCG can be explained by things that aren't necessarily related to chromosomal abnormalities. For instance mine was above average at 1.81. I have high bHCG in early pregnancy too - apparently the two can be related.
Bleeding and IVF pregnancies can make you more likely to screen positive as well.
I am exactly like you when it comes to the prospect of a child with Down Syndrome. I don't have a bloody clue how I would cope, but also I could never (personally, no judgement on anyone else) terminate either. I read up a lot on children with Down Syndrome when I was waiting it out and got a lot of mixed messages. It seems so much depends on the "severity" it presents with. Some children are absolutely fine, can live normal lives.. but at the other end of the spectrum, may need 24/7 care. Unfortunately there is just no way to know what you're getting. A significant proportion also have heart defects (did they check the heart? although it is too early to spot everything) but most can be corrected with surgery.
I can understand your DP hiding but I wish he would come home to you
Did the hospital discuss next steps? If you're close to London, the Fetal Medicine Centre is the "go to" place for dealing with stuff like this as it is run by the man who invented the NT scan in the first place. I went there and they did such a detailed NT scan I felt very reassured. Obviously some abnormalities won't show up until later, but there is still an awful lot they can check for at this stage too that an NHS scan won't even consider. They also redo your bloodwork and you get results right away as they have a lab on site. It's £180 for the NT including bloodwork.
There is also Harmony, which is around £400-£650 depending on where you go. It's non-invasive, and provides as close as you can get to a diagnosis (either 1 in 2, or 1 in 10,000) as you can get without invasive testing. Sadly it's not quite yet available on the NHS, and also it takes two weeks (getting my results on Friday for this DC) Not everybody knows about Harmony as it is so new, so do bring it up with your midwife if she doesn't.
Then of course there is the CVS/amnio route. I wasn't brave enough to go down that route as I couldn't live with myself if I miscarried as a result, but most people are able to make that decision. I might have made a different one if I'd been 1 in 5, I have to say. The need to know and all that. I had a late "safe" amnio at 32 weeks last time (no Harmony then!) where the risk of preterm labour is the same as the earlier risk of loss just because I needed to know before the birth.
Very much thinking of you! I was in a right old state to put it mildly (on my own as well) when I got my odds of 1 in 34, so I can't imagine how you must be feeling.