So are you just wanting to go to a maintenance level of strength? If so, you can get buy with a one day per week, and then follow a
power running type program .
Mon - Strength
Wed - 5k
Fri - Intervals (100's, 200's, 400's, 800's whatever). Just try all the different distances, more distance = more recovery time, then over the weeks decrease the recovery. You can even mix and match the distanes, e.g. Run 800, rest 3 minute, run 100, rest 30 sec., run 400, rest 1:30 min, ect.
I put the strength day after 2 rest days because you seem more concerned with not getting weak during this whole thing.
Or if you want 2 strength days:
Mon - Strength
Tue - Intervals
Wed - Off
Thursday - Strength
Fri - 5k
Sat/Sun - Off
Again, I put the strength after rest days since you seem to not want to get weaker.
I also like Mike's idea of not doing 5k's every week. You could change all your running to sprints with long rest and the short rest intervals.
You could also exchange some of the interval days with CrossFit metcons that include a run in them.