Kiln dried sand is available from any builders merchant - As the name suggests it is dried sand, and very fine so it can be swept between the joints of block paviours, different to normal building (yellow) sand.
Cigarettes have a big warning on them that its bad for your health but it does stop most people. I don't see the problem with kiln dried sand used as a blasting medium, i would be more worried about the lead in the paint your blasting off. Just wear suitable resperation equipement and be sensible, like don't do in an enclosed room without good ventalation
I do a lot of glass sandblasting and i was always told never to use sand,it was banned from use for blasting as its very fine to start with and it breaks down to almost a powder which is very very damaging for your lungs,there are quite a few companies that supply blasting media,its normally in 25kg bags but sometimes smaller quantities.
I've got one of those cheap suction guns, ok for very light use but not much else. You need a pretty decent air supply for blasting, lots of CFM and DRY air only. I use ali oxide grit in mine, it's reuseable several times as long as you sieve it.