Trying to Conceive: 6 Months, Still Trying Community

Hi I am 35 yrs old. Me and my husband trying for our second child for last 4 months. I just got my period again this month Feb 9, so disappointed. My ovulation varies between 24-27 days, my first days of period for last four months :
October 30, 2012
November 26, 2012 : 27 days cycle
December 22, 2012 : 26 days cycle
January 15, 2013 : 24 days cycle
February 9, 2013 : 25 day cycle

Being frustrated by this irregular cycle, in after January period I bought the "Clear Blue Digital" ovulation kit. My period was Jan 15-Jan 20, so I start testing started Jan 22 once a day everyday around 2:30PM. Got my first positive on Jan 24, so we intercourse Jan 24, Jan 25, and Jan 26.So my questions are :
1. I test jan 23 not position, then 24 hrs later jan 24 got positive. The box says ovulation may occurs 12-36 hrs later. What if LC surge was actually 23 night, and by the time I tested positive again 24, the ovulation done. Should I test every 12 hrs?

2. After the positive test how many days a women can be fertile?

3. I was thinking intercouse exactly 3 days after my period ending, is it a good idea or that would be too early for the spem be alive?

4. Could pls give me some suggestion about this month ovulation and fertile period based on the calender I provided above. Yes, I am using the webmd ovulation calender and all sort of different apps, but still confused.

Thanks in advance. I am in distress, pls provide me any kind of direction and advise. Thank again!!!