We used to keep Jacobs but no longer do. They are beautiful animals, full of character, which is why we chose them initially, but we found that they no longer live up to their previous reputation of being good lambers. They have been bred to be ever bigger - ours frequently had triplets and almost invariably one of them would be backwards, making for a variety of complicated lambings. They are hefty girls and as we grew older we found them too heavy to handle. How easy they are to drive, get into a pen etc depends on your system and your own skill - there will be wild ones and very friendly ones.
We only ever crossed ours with Shetland, Hebridean, Texel, all of which gave lovely meat and good sized carcases.
I would expect that using a CM tup would give a smaller lamb which should do away with some of the lambing difficulties, so definitely worth trying

The lambs should be mostly black.