If it's acrylic it is a topical and you should be able to tell by it's yellow, waxy, blotchy, peeling look. If that's the case you will need to use a stripper. I don't see a topical in the pics but it's hard to tell. you can scrub it I use a carpet brush on a low rpm swing
For pressure 1200 psi works good and will not harm the stone, since it is a kitchen a degreaser will do the trick. a good impregnating sealer is what this floor needs. sandstone has large pores so a sealer with large solids is best. stonetech bulletproof is a good one and is easy to find. and apply. As far as water base goes My opinion is they work just as well as a solvent base if the floor is dry and is applied properly. Durability has nothing to do with water base or solvent base. Water or solvent is just a carrier for the solids. It's what the solids are made from that is important. Your right this will clean up easy. how you seal it will determine how well your work holds up.
Below is a copy and paste (because I'm lazy) to help you understand stone sealers a little better.
PS. Please do not put topicals on stone. The homeowner will regret it down the road and you can bet they'll remember who did it
Topical sealers
Generally made from polyurethanes or acrylics. These sealers may be effective at stopping stains but, being exposed on the surface of the material, they tend to wear out relatively quickly, especially on high-traffic areas of flooring. This type of sealer will significantly change the look and slip resistance of the surface, especially when it is wet. These sealers are not breathable i.e. do not allow the escape of water vapour and other gases, and are not effective against salt attack, such as efflorescence and spalling.
Penetrating sealers
The most penetrating sealers use siliconates, fluoro-polymers and siloxanes, which repel liquids. These sealers penetrate the surface of the stone enough to anchor the material to the surface. They are generally longer lasting than topical sealers and often do not substantially alter the look of the stone, but still can change the slip characteristics of the surface and do wear relatively quickly. Penetrating sealers often require the use of special cleaners which both clean and top up the repellent ingredient left on the stone surface. These sealers are often breathable to a certain degree, but do not penetrate deeply enough (generally less than 1mm) to be effective against salt attack, such as efflorescence and spalling.
Impregnating sealers
Uses silanes or modified silanes. These are a type of penetrating sealer, which penetrate deeply into the material, impregnating it with molecules which bond to the cappillary pores and repels water and / or oils from within the material. Some modified silane sealers impregnate deeply enough to protect against salt attack, such as efflorescence, spalling, picture framing and freeze-thaw spalling. A good depth of penetration is also essential for protection from weathering and traffic.
