A few violets do like lime in the soil, primarily those types from naturally limestone or shell-sand areas. But for many species/cultivars a slightly acid / neutral / slightly alkaline soil is fine. The soil acidity can affect soil-borne pathogens, though, which can add a bias to what is best. Your "sandy, moist, shady and acid" soil would not exactly be my first choice for violets, but you talk of some species apparently finding it to their taste, and I would be happy for the plants themselves to be the best arbiters.

Your V. odorata var. sulfurea (the apricot one)...
For me it does seed itself about, but not as much as the violet or white varieties. But that may just be a reflection of the fact that I had much more of the violet and white ones. As far as I am aware, it has the same cultural requirements as the other colours. However, it is the rarest of the basic natural colour varieties of V. odorata (violet, white, pink, apricot; and there are various purples and purplish-whites), so this may have an effect even on a scale as small as a garden; the mechanism is unclear, though.

If in doubt, collect some seed of the apricot one and grow plants for 1 or 2 years before planting out. (Collect it whenever you see the seeds tumbled out of the pods onto the soil, if the ants don't get there first.) That may help establish a critical mass - sufficient for self-sowing to perpetuate thereafter. You can propagate it by runners, too.

Thanks,Mike. Does not seem to have many runners. stayed as a forlorn one or two by the front concrete step before I redid the front walkway. Also a one or two by the back. This week I noticed a single flower at the base of the rock garden. Had moved it there before I tore out the old front walkway. Will keep an eye out for other flowers and any seeds that form. The few flowers make little impression. The white is quite nice for a week or two.

My apricot violet is from the same place - I think I bought it as "Vilmoriniana". Mine is very happy under a hemlock tree, not very moist at all as it's on a slope and heavily shaded from rain. I've moved some under a Japanese maple to see how it works - much richer soil, much sunnier, but more likely to get watered. So far, the ones under the hemlock have spread by seed and runner into the lawn, and erratically around the tree, where they share quarters with Omphalodes verna and a bunch of Primula veris cultivars.
From your comments, I'd say that perhaps it *doesn't* like lime, and perhaps would be happier in an area way away from concrete and the like. At any rate, that's what I'd try, if it were here.

Thanks so much. So good to be able to contact people with a passion for plants and formal education about them. It was purchased as vilmoriniana and I will move the few i have to various places, hoping some will multiply better.