The record to SD card can be triggered by digital input. To answer your questions:
1) The recording length is unfortunately one of the bad things about the firmware. The DLink firmware will break up your files into multiple files based on the time of the day. With default settings if you record a 1 minute video starting at 1:59:59 you will actually get 2 files. The first file will be 1 second long (1:59:59 to 2:00:00) and the second file will be from 2:00:00 to 2:00:59. Idiotic. That is clearly intended for the "Always" trigger record mode, and does not make any sense for any of the other trigger record modes and there is no way to turn this behavior off.
2) You can send a video OR 1 snapshot OR a series of 6 snapshots to email addresses. Choose one. I am not sure if it is possible to send to more than one email address - you may be able to enter multiple email addresses separated by commas, but I have not tried this.
3) You are probably referring to viewing the SD recordings. You can only download them using to a PC via a clunky interface. There is no way to view SD recordings on other kinds of devices (iPhones, etc). The direct web interface does not work on mobile phones.