Definitely wouldn't keep a tup indoors with lambing ewes.
In cattle, the pheromones around calving time are similar to those when they're bulling, so other beasts (males, whether castrated or not, and females too) can start wanting to mount them. I wonder whether there is a similar thing with sheep, and that's what makes the males chase the lambing ewes about?
We do sometimes leave Texel tups with lambers outside, and in fact one of our tups is called Big Daddy because he protects the flock, especially the lambs. (Awwww
) Texels are generally so lazy they only move for feed, really, outside of the tupping season.
You could see if the tup would behave himself with lambed ewes? Assuming you have a field you are putting ewes-and-lambs in once they've mothered up. But if he bashes the lambs, which he may do at feeding if not at other times, he'll have to go where he can see and smell other sheep but not be with lambers or lambed ewes.