1. Unfortunately, it will not do both. One or the other.
2. If you are going to do videos, I would recommend the max which is 2GB. 1GB will do just under 1000 MB. Take a couple of test videos at 60 sec, look at the card on your computer and see how many MB average you are getting per session. It varies slightly.
3. 30 seconds should be fine. Depending on traffic, you would adjust that to your specs. I dont recommend having the intervals too close together. I have done that before and traffic was high and the card filled up way before I was able to go back to retrieve it.
4. When you say red lights. You mean the IR leds? If so, they need to work to get the night pics. It would be a soft glow visible at eye level looking straight at it. Once you angle a bit, you dont see it. The center flashing red light is when it is in that 10 second set after you turn on or remove the remote for it to arm or while you are programming it. Not while it is armed in the field.
Hope this helps. Let me know if you have any further questions
Joe