All of these things happened because of Dan's infidelity:
-Numerous harrassing calls to the house -The house was broken into and their rabbit was boiled -Daughter was kidnapped from school -Their family car had acid dumped on it -Beth got into an accident while searching for the daughter and was hospitalized -Alex breaks into the house and attempts to kill Beth
I suspect that almost losing her life as a result of the accident made her re-evaluate things. She believed Dan when he was sparse with the truth regarding his "affair" lasting but one night. But he had no intentions of extending their liaison - Alex pushed him into that Sunday meeting and he seemingly felt a misguided sense of obligation.
Beth was not earning either so there was a financial incentive plus they had a precious and much-loved little girl together. There's nothing quite like a nasty car accident to make people re-evaluate their lives. He was a fool, on that we can agree but Beth was a very understanding wife in the end and took her disgruntlement out on Alex, eventually. Perhaps she came to the conclusion that Dan had already suffered enough with the ongoing threats and Alex's taunting that you listed. We weren't witness to any huge conversation about the extent of Alex's vengeful actions but I imagine it was discussed. Beth could see he was remorseful and she was injured and vulnerable. The way he clasped her hand and nestled up to her in her hospital bed was very telling of his regret.
Also at this point, crazed Alex was also still out there and Beth probably felt Dan was better off moving back in - if only to keep her and their daughter safe.
"These days you have to boil someone before you can sleep with them"
Beth came off the worst and she was in a sense the innocent party. At the same time, she would have also grown and become more resilient from her experience. I doubt she would have taken things for granted so much in her life, after the Alex attack.
Have you seen the alternate ending your High Grand Holiness? ✨ Beth is still seen dedicated to Dan and it even ends with her finding a way out to prove Dan's innocence by listening to the tape Alex sent him. She says to Ellen, something like..."Let's go get daddy". I think Dan was very lucky to have a lady like Beth in his life and if Dan was smart, he would also start to fully acknowledge and appreciate what he had in his life too.
Exorcist: Christ's power compels you. Cast out, unclean spirit. Destinata:💩
Yes, I sure did see the alternate ending and was actually discussing it on a thread here recently. Glenn Close vied for that particular ending as she felt it would be a more fitting and a truer end for someone in Alex's state of mind. She was apparently quite adamant but they went with the first one anyway which to me was more tense and dramatic. It also of course saw Beth carry out her threats of "If you come near my family again I will kill you.."
I think it's on the Special Features of my DVD.
"These days you have to boil someone before you can sleep with them"
Those things were not a direct cause of Dan's indiscretion, but due to Alex. Beth didn't choose to stay with her husband after wrestling with Alex's behavior, but the infidelity itself. Why would Beth blame Dan for the car accident, of all things? Back in more rational times, we didn't blame everything due to cause and affect (especially men)
Although it wasn't shown in the film, I think Dan told Beth everything from start to finish, including how he attempted to end things with Alex but she wouldn't stop. That's the ONLy way I can understand Beth staying with Dan after all that happened.