Hi,
Just my opinion on your queries are:
Answer to 1st Question: You can not create the invoice schedule time-frame different from the contract start date. you create first two schedule in first schedule time frame and rest you keep monthly( for example your contract start date is first of Feb and you can not start invoice schedule from 1st of Jan, but you club Jan and Feb invoice and start from Feb first)
Answer to 2nd Question: You can change the Automatic invoice run time Horizon in the Fine-tunning, By default it set for 3 days you can change accordingly.
Thanks
Vinay