My dogs had a bad fight, what can I do?

I'm fostering a dog from the shelter and was considering adopting. She was spayed the day I was able to bring her home, so she was kennel kept in order to heal (per shelter recommendations) for about a week. I already have a male (unaltered, he had parvo when I adopted him) in my home. I passed on here their first "encounter" without a barrier. He had his hackles up the entire time and I ended the 3 minute session when I noticed it.

Over the course of the following week I kept their interactions only outside, only 3 to 5 minutes and always supervised. I always picked up all toys, even sticks, food bowls, etc. before letting them engage. His hackles finally subsided and he even seemed to be submitting to her (in a way). That went on without incident for 5 or 6 days. Then about 2 weeks ago (she has been in my house 3 weeks at this time) he attacked her. I had noticed his hackles were back up and that hasn't been an issue for the last 4 days. She submitted, screaming and laying on her back. He stopped for a split second, didn't break his eye contact from her and then went back in again. He drew blood, when I finally got him to stop his mouth was full of blood. I thought he bit his own tongue to be honest because they're wasn't blood on the ground and she has a lot of hair. She has scabs on her cheek and by her ear. I seperated them. Someone adopted her from me that evening. He had been inquiring about her prior to incident. He had her for 2 days and returned her. She wasn't the right fit for his lifestyle. She needs a little training in chewing and more supervision than he was able to give her.

So she is back with me for about a week now. I have kept them seperate. She stays in a kennel in my room at night. So they do see each other through the kennel. There hasn't been any growling or hackles. Male loves being outside, not her so much. So I've been able to keep them seperated easily during the day. It is starting to get cold and I can't leave him outside during the day anymore (even though I think he still wants to be outside mostly). They are both 60 to 80 lbs. My husband passed last year and I have an autistic 19 year old who physically wouldn't be able to help if something were to go down again between them.

I am posting the video because this was the day before he attacked her. I obv don't have video of the attack. I realized there is a plastic bowl my male prefers over any other toy (lol, I know it's odd) that I didn't pick up. I was worried it might be an issue, so I ended that video with a "no" when she reached down to get it. I picked it to immediately and there wasn't an incident, that day. She nips at his face constantly and he isn't crazy about it as you can see in the video. She also constantly tries to mount him. I've been spending time with her trying to let her exercise some of her anxiety away, but she doesn't know how to play fetch or play with anything really. When I throw the ball she gets excited and runs after it. Then she looks at it and comes right back without the ball. I know it's not her fault, but i am at a loss on how to help her with that. What can or should I do? I am willing to put in the work. I already love her. Short term what I've been doing has worked, but it def isn't a long term solution. I read somewhere, I think on here, that once a dog draws blood on the other dog that bond isn't repairable or can be almost impossible to fix.

In case it matters according to the shelter his mom was pitbull and boxer. Didn't know about the dad, but obv shepherd or maybe husky? He is 75lbs. His collar is gray in video.

Shelter said she is Beligian Mailinos & Shepherd or Whippet mix. She is still gaining weight but she odd about 65 to 70 lbs. Her collar is blue in video.

Any constructive criticism or advice is appreciated. Thanks guys!