Just a thought - land which has had pigs on will have a high copper content - copper is toxic to sheep, so I would suggest getting it checked out before putting your livestock on it.
For breed, the primitives are small, light on the land and do well on poorer quality pasture, but purebred lambs can take 16 months to reach slaughter age. If you choose a crossing sire carefully, you would get the benefits of primitives plus faster finishing lambs, by the end of the first year, so no overwintering of lambs, which helps conserve your grazing.
An acre will seem huge at this stage, but the amount of land needed to keep livestock healthy is more than you would think. Sure, when you put your 5/6 animals out they will have loads of grass if the land is good, but they will quickly eat it, then what will you do? Overstocking really is a mistake, as you will only produce miserable, puny lambs which will not thrive, and you are likely to get a build-up of parasites in the soil. Anyway, with such a small area you will need to supplement winter grazing with ad lib hay, plus some hard feed.
I wasn't sure what you meant by rotating stock - it usually refers to moving your flock to fresh ungrazed fields regularly through the year, to make best use of grazing and avoid parasites. With only one acre you can't do that. If you meant how do you replace old ewes, it depends on the breed and whether you are emulating commercial breeders' methods, or whether you see yourself as a smallholder. Many smallholders keep breeding from their ewes until they loose their teeth, then they replace them with their own daughters. Any ewes which have to be culled before they are too old can be used as mutton, which is delicious.