Page 1 of the link suggested by jimates contains a digit map worked out by RonR, so most of us cannot improve on that
However, with your configuration having FPL on sp1, then you need to set:
Physical Interfaces -> PHONE Port -> Primary Line : SP1 Service
RonR's digit map will then need to be on Service Providers -> ITSP Profile A -> General -> DigitMap
Also, where RonR uses <**1> you should use <**2> to direct long distance calls out to
voip.ms on sp2.
If at some future date you wish to swith to voip exclusively, then you may need to consider changes to Phone Port OutboundCallRoute to direct services such as 911 to sp1.
Good luck! Let us know how it goes.