What type of marble?
Test to see how porous it is.
You will be fine with 511.
I use paper towels ,pour a small amount of product on the surface and spread it out over an area you can reach.
Let it load into the stone for 10 minutes and wipe all the residue from the surface.this is the crux.do not let any sealer dry on the surface.period
The surface area you just did should be completely dry of sealer(it lives below the surface) then just move on to next section and repeat the process.
Wait 24 hours and water test. If it still absorbs do another application.
Yes cover the tub and floor.

Thank you for the follow up srosen. The tile is not very porous because I had left some cuts in the water tray of the wet saw and when I cleaned them out they were no heavier than the dry ones. Thanks for sure about not letting it dry on the surface.