Join Date: May 2008
Location: The Mangroves, UK
If it's a Dahon Speed D7, it's square taper. Use a crank extractor to pull off the crank, put chainwheel in a vice and gently persuade back into shape with a rubber mallet. If it's so bent it snaps, you've lost nothing. Once straightened, its weaker than it was.
Paint chips? It depends on how pristine you want the bike. My local street market sells nail polish in every colour, it's good for touching up minor spots. Car paint touch-up sticks work, too. The toy store paint willl be fine, it doesn't need a top coat, but you can add clear coat over it. (Car store - just mention paint chipped.
If you want to replace the chainwheel, the French Stronglight ones are available in a bunch of square taper sizes. (They are used on Bromptons). Brompton cranksets may also be suitable and come in two teethings. You may need a longer chain. Otherwise, your local Dahon dealer is your friend.
Regarding the low first gear, if you change the chain wheel for larger one, you move all the gearing up and need a new chain. The real question is; is the 'hardest' gear not long enough?