getting the guys together
If it's helpful, I encourage your hubby to take the initiative to get a good, sit down conversation going with J-kun. This is something I've (the male half) learned is really important right in the early stages. Men are subject to the same pressures as women in this regard, and it's stretching outside the comfort zone of most men to have conversations relating to being sexual with the others wife. But it's a conversation that needs to happen and your hubby is the one who is in the position to have to take the first step.
Once that happens the relationship will be poised to evolve in the direction it will - whatever that may be. But until it does there's going to be more discomfort in the whole triangle than there should be which will over time put stress on it.