I had a massive bilateral (saddle) pulmonary in 2018 - "massive" being a medical term rather than me being dramatic. It also caused right ventricular strain caused by the back up of blood in my heart. Mine was caused by a recent major leg surgery, so it was what they call "provoked". It sounds like yours may have been provoked by a combination of the HRT and virus.
I was in resus, then ICU for some time and had an IVC filter put in to stop any more of the DVT breaking off and travelling up to my lungs. Like you, I was very close to death, and was asked some very scary stuff in resus, such as "do you wish to be resuscitated if your heart stops?". The plan of attack was to give me the clot busting drug, but my orthopaedic surgeon told the resus team that he would have to immediately amputate my leg if they did as I'd have died from blood loss from the recent surgery (only a few days prior), so they essentially hovered over me with the drug watching the monitors in readiness to give it to me if I deteriorated further, fortunately the heparin and my body managed to deal with it. Subsequent Drs went white as a sheet when they saw my initial scan; general consensus was that I shouldn't have survived it.
I was eventually sent home on Rivaroxaban which I was on for 6 months (I guess you may be on blood thinners for longer if there's any question over the cause, mine was pretty clear cut). I am now essentially fully recovered, albeit some scarring on my lungs which makes running a marathon impossible, but day-to-day life absolutely fine. I was very worried about something called CTEPH (Chronic thromboembolic pulmonary hypertension) as long term complication but that didn't happen, and actually I was at low risk for developing that looking at the risk factors. Unlike normal pulmonary hypertension, this is something that is treatable though.
The biggest issue I had with recovery was the mental side of things, I developed pretty debilitating depression and PTSD which I ended up seeing a psychotherapist for some time for. Something called EMDR (a form of therapy) worked really well for me, as did a lot of meditation.
I was told I have a greater chance compared to the rest of the population of having one again, but it's still a very small likelihood. Although not on blood thinners anymore I make sure I take aspirin and wear compression socks if I'm flying or going to be sedentary for any significant amount of time. I also eat quite a bit of fresh pineapple (was mainlining it when I got home from hospital!) as the enzyme it contains (Bromelain - the thing that makes your mouth feel funny when you eat it) has been shown to break down clots. Have not had another since (touch wood).
I absolutely empathise about the fear of what's going on inside of you, it is debilitating. I'm happy to talk further if it would help at all. Sending you lots of positivity and clot-busting thoughts.