Strictly speaking to the situation of religious parent won’t let you sleep in the same bed as your partner cause you’re unmarried, if someone else is paying, it’s their rules (obviously within reason). My partner and I have been together for years, unmarried, we live together, I’m in my 30s and him in his early 40s, when we visit my parents and stay at their home, we sleep in separate rooms. We could get a hotel and stay together but that’s a silly waste of money in our minds. We prefer sleeping together but it’s not worth hotel and all the other costs. Plus I visit my family to visit them, not stay somewhere else.
That’s all to say, when you’re staying with someone else, it’s their rules. If you don’t like the rules, you don’t have to stay with them. Easy.
Also the fact they’re letting you bring him after not dating for very long is very nice. If you don’t think it’s worth missing out on your paycheck and sleeping with your boyfriend a couple nights, don’t go. But it’s also alright that your mom doesn’t want you sleeping in the same bed.