AustinScoobee writes:

1. Do we need to remove the paint from the slab? It is very well
adhered but would come off with a razor scraper and alot of sweat.

Yes. Use a chemical remover.

2.. Does marble have grout lines? The floors we've liked seem to not
have any gap at all

All tile must have grout lines, unless you have geometrical perfection
(tile size, squareness, floor flatness, thinset bed thickness).

3. How does it wear? can you slide a chair across it without
scratches? Does tracked in pebbles or sand scrath it? Does it scuff
with black shoe marks?

Marble is very soft and brittle. Scratches easily.

4. It apparently needs re-polishing from time to time, how often in a
residential install?

Diamond polishing is needed to cure initial lippage. How often for
looks depends on your traffic.