Yes, this is unusual. "Can't have sex with my male or female partners until I break up with outside lover, or somehow bring outside lover into the cult *cough* group."
Generally, safer sex is practiced in poly circles by using condoms with lovers, asking for current test results, and open communication about past sex practices with new person's former or current partners. None of this "no sex with my other partner(s) until 'incubation period' has passed" deal.
We do have recent threads here about safer sex, herpes, etc. Do a tag search.
Sounds like you have a good life, family, thriving career. Who is it wants or needs to move your group across country? Let me guess... the male.
BTW, even if you found a bi male lover, there's no guarantee he would be attracted to your Leader/Dom/Lord/Sir, or vice versa. Just because someone is bi, doesn't mean they will shag anyone of either gender. If you want a bf, and want him to be straight just so you're sure he's yours and not a new pet for your Leader, go get him! If this doesn't sit well with the rules of your current polycule, YOU decide what to do... weigh your options and potential benefits.