Re the sail.
There should be a bungee loop at the bottom of the sail - hook this to the fitting provided on the boat just below the mast base - this stops the sail & mast falling off if you turn turtle with the sail up.
The lead of the rope that you use to trim the sail (the "sheet") looks just about OK in your photo (from what I can see of it). It should go from the "clew" of the sail to the padeye in front of the rudder at the stern of the boat then along the deck to the cockpit...
Most advice you will find here (including my own) is that you should used very small free-running "blocks" (i.e. pulleys) to reduce friction in the sheet so that if you let go of the sheet when sailing, the sail will de-power as quickly as possible (this helps prevent a wind-driven capsize). Get marine blocks (Ronstan/Harken or similar) - such as used on small dinghies - and the smallest ones you can find should do the trick - don't get ones with swivels as these tend to twist & lock your lines.
I recommend 2 blocks: one on the rear padeye (the sheet runs through the block rather than the padeye!) and towards the front of the cockpit on one side or the other (I think the RHS works well on the OB). The sheet then comes forward from the rear block to the front of the cockpit, through this block, and back to the helmsman's hand. This way you pull on the sheet to pull the sail in - which I find more comfortable & natural than trying to "push" on the sheet to pull the sail in (which is what you have to do if you do not have the forward block).
You may have to replace the standard sheet, if that is what you have, with a longer piece of rope to get it to reach forwards & then back & provide enough length to let the sail out and pull it in. You don't need any kind of fancy & expensive low-stretch yachting rope just get something nice & floppy -preferably not three-strand rope though, because it tends to kink & then may not run cleanly through the blocks when you need it to - the loads are small so just about any line will do but you will find that if it is too thin it will be tiring to hold so get it thick enough that you can grip it but thin enough that it will run freely & cleanly through your blocks without "choking".
Don't worry about getting fancy fittings or drilling holes to attach these blocks - just tie them on to an appropriate fitting with a few loops through of light line of your chosen colour so that the blocks can move reasonably freely - the loads are tiny so there's very little risk of the line breaking and that way you save $ and you can always untie them to move them if you want to.
If you haven't sailed one of these before choose ideal conditions until you know what you & the boat can/can't do.
Re the scratches:
Leave 'em alone & forget about them: they're on the bottom. One of my boats (2nd hand I should add) had been dragged over oyster beds & the bottom had deep gouges in it. Didn't look like much but wasn't a problem. I used a water blaster to clean the grime out of them & then you could hardly see them. don't sand - you will thin the hull and introduce tiny little scratches which are just as/more unsightly & would be very difficult to polish out - and in any case you now have better things to do (like going sailing).
Enjoy.
P.S. I really like the look of your boatshed - complete with sail loft & testing tank - and I like the cunning transparent weather-watching panels - I'm very envious