A ram will be fine with a wether once they have worked out their pecking order, the ram will almost always be the dominant sheep. When I add another ram or wether to an existing ram flock, I will then move the herd around for 10 minutes or so with a herding dog so that their attention is kept focused on the threat of the dog rather than on the new arrivals until they have had time to coalesce into a flock. I don't have an electric fence, but a field fence won't keep a ram out for long if there are in-heat ewes teasing him on the other side of the fence, they can tear it up in less than half an hour, but horse (no-climb) fencing will keep them in. A horned ram can even batter a pole gate into a pretzel to get to a ewe.
The best way to keep a ram(s) separated from a flock of ewes or ewes with a ram is to keep them at least one field away from the ewes. Alternatively add an additional fence parallel to the existing fence line, so the two fence lines separated by at least 6 feet. This way the in-heat ewes can't press their butts up against the fence where the ram can sniff them and be goaded into making strenuous effects to get into their field.
A ewe about to give birth will often move off from the rest of the flock a few hours before giving birth. If you
feed your sheep, you can also control the time of birth by when you feed them.
If you feed them at 8am, then almost all of the ewes will give birth between 6am and 1pm. Doing this, I haven't had a night birth for several years. If you feed in the late afternoon, then most of the ewes will pop during the night.