Hi Kay and thank you for this new question.
I'm really sorry you've been dealing with this issue, it sounds incredibly stressful.
It sounds like she becomes highly anxious and territorial when seeing another cat, so goes into fight or flight mode, and you are the unexpected target of this. It is not aimed at you, but you are getting the brunt unfortunately.
I agree with blocking her view of other cats for now, as we want to minimise her anxiety. It can be really useful to buy reflective sheets that stick on to the windows.
I'd also aim to reduce her anxiety in general.
Try to tempt him by playing with fun toys (laser pointers, wind up mice, string) and offer food puzzles and other interesting things to dol. The more occupied and busy he is, the calmer he should become.
I'd be keen to use calming products, as these can help to some extent.
This would mean a Feliway Friends plug in as well as some natural calming supplements such as Zylkene that go in her foos.
I'd also wonder if he may be at the point where prescription anxiolytic medicine like Fluoxetine (which the vet can prescribe) are worth starting her on. These really help to get that anxiety level down.
If she has not shared her home with another cat before, she may find this very difficult.
This website is an excellent resource:
https://icatcare.org/advice/introducing-an-adult-cat-to-your-cat/