It is not practical to delete that default route and
replace it with some 
200+ individual routes
The opposite approach may also be possible if your upstream network
operators are up for it.  You could leave the /8 route as it is today, but
setup a BGP filter that propagates the more specific internet-based 44
routes to your upstream devices.  This would allow the gw to remain a
catch-all for research purposes (if that's still a thing).