Hi,
 
I am just going to throw this out there for consideration.  I really need a prophecy partner to bat this around with, but since I don't have one, I guess I will use the Doves....O.K?
 
Maybe the "Great Tribulation" starts immediately after Daniel's 70th week.  Seal 6 is the beginning of God's wrath, and the sealing of the 144,000.  Does this indicate that the 144,000 have come to Christ?  They will be protected during the time of God's wrath, so maybe the 70th week has accomplished it's purpose.  It is my understanding the God's wrath is for the unbeliever, so why would His wrath be visited upon Israel before God is through dealing with them, and before the 70th week is complete?
 
This way, Jacob's trouble could have started in 2000, and when it is over, the great trib starts.  That would leave plenty of time for the things that take 3 1/2 years to take place.  I would guess they (all of the different 3 1/2 year periods) could run at the same time.  Some people have said 2012 as the final year, and this would fit in that time period.
 
BTW, does any one have an explanation as to why the Bible lists these different time periods differently?  Such as: days, sometimes, months, and sometimes years?