I can see trying the no-PIV rule for awhile, but check in with A frequently to find out when he thinks he might be able to let that rule go. Basically, as soon as he thinks he can stand the change, I would implement it. As shown in the other posts, a no-PIV rule can get complicated fast.
I sympathize with how hard it is to overcome religious conditioning. I was raised staunch Mormon and my brother-husband was raised staunch Catholic and ideas like polyamory were just so far out of the realm of thinkability that both us guys had to move through some major personal trauma before we could finally stand to share a woman (and even then, we had years of drama to slog through before our V relationship really found its sea legs).
Do the best you can. The LDR factor with M and T does give you time to think (and talk with your husband about all this stuff).
Love means never having to say, "Put down that meat cleaver!"