Garmin Etrex 30 -

The 250 point limit is fixed. I believe that your options are to use BC to filter the route to less than 250 points or split the route into shorter lengths each with less than 250 points (e.g. split a multi day route into separate days) or convert the route to a track.

No, as pointed out 250 is the limit for a direct route, it's only 50 if you've selected a routing activity.

For longer routes either split them or convert them to tracks as suggested.