Scratches are fine; a long time back Formlabs even thought about sending the platforms pre-roughened in order to improve adhesion of your parts.
If you’re worried about keeping the platform smooth you could buy a Removal Buddy.
how long after washing in isopropanol, must a print dry, that the resin is fully hard ?
i know i can speed this up with uv light and the form station, but i mean without that help?
You should let the part dry at least 30 minutes. I let mine dry for a couple hours before curing. This ensures all the alcohol has evaporated and any swelling due to alcohol absorbed by the part during the bath has had time to subside.
You don’t want to UV cure until it’s completely dry.
As for breathing protection, it really depends how ventilated your space is. I use a 3M half-mask respirator myself, like the one pictured in these links:
3M Respirator (Amazon.ca) with 6001 black or 6003 yellow (Amazon.ca) organic vapor filter cartridges (for isopropyl alcohol fumes, unless workspace is well ventilated)
ps. Some more introductory tips are here - I made that article for the Form 1+ but some of it may answer questions related to the Form 2 as well.