Here is a couple of things:
You can manually edit the schedule (League Set Up) to add more games for your first season.
You can play out the first season as is and generate a new schedule with whatever you decide as the amount either with the In Game Schedule editor or Stickwares schedule editor. The latter I'm sure can be downloaded at:
WWW.OOTPLinks.com
For 20 teams two division I would go with 154 myself used from the early 1900's ( I think '04 or '05 LeGrande???) until 1961.
I wouldn't worry about the records being smashed after only one season.