I have a few general questions I hope someone can answer:

1) On average (maybe someone who has done this often can answer) If I check in lets say 23 hours and 50 minutes before my flight, would I expect most seats to already be claimed, or can I assume that I will get whatever seat I want. I just want to know if I need to sitting at my computer exactly 24 hours before and need to rush to book the flight seats.

2) If I have booked a flight from JFK-TLV through LHR, can I pick my seats for the LHR-TLV segment when I check in for the first flight, or will I need to do that separately 24 hours before as well. And if I have to do it separately and my London flight leaves 8:30AM London time, will I have to go online at 3:30AM EST to book it, or 8:30AM EST?

3) If for religious reasons I cannot book my seats 24 hours before (when I leave Tel Aviv it will be a Sunday morning and I cannot go online Saturday morning), is there any chance of me being able to book this earlier if I am just in coach with no status, or will I either have to wait until I am able to go online or just get a friend to do it for me.

4) I am traveling in March (4-15), is March generally a slow month to travel to London or should I assume the flight may be kind of full. I am leaving on a Wednesday night and returning on a Sunday.

5) Is there any way to upgrade with AA Miles, and if yes, please give details or direct me to the webpage.

Thanks!