To answer to BGP problem about BGP and static route (big subnet) to Null 0 : http://lacuisinedegandi.net/post/2011/06/20/Quand-Null0-et-BGP-peuvent-causer-probleme.

A solution can be :

R2#sh run | inc track
track 10 ip route 217.169.255.1 255.255.255.255 reachability
ip route 217.169.240.0 255.255.240.0 Null0 track 10

Where 217.169.255.1 would be IP of loopback IP address of an iBGP/Transit eBGP router. So that, if it is unreachable, static route to 217.169.240.0/20 will be removed and announcement to an eBGP neighbor will not be sent.