If you haven't seen my post check out
http://singaporeexpats.com/forum/ftopic38927.html
For your questions:
1) If you do not elect to get a Singaporean nominee director, then you cannot form your company until you receive your approval in principle letter. Then the company can be formed within a few days.
2) If you do have a nominee director, then you can form your company a maximum of six months before the approval of your EP.
3) And Entrepass can take anywhere from a few weeks to 3 months or more depending upon the business and the quality of your business plan. If you have tentative contracts be sure to include this information in your business plan.