Hanover Rd behind Whippany park HS
have you checked google maps bike routing? i just punched in pub 199 and whippany park HS and got a route that is only 18 miles, mostly downhill, doesnt use columbia tpk, doesnt use rt 46 (crosses it tho) and is only on rt 10 for a short period(and actually looks like it could be avoided with a cut through dickerson mine based on comments above).
not sure about sussex tpk or hanover ave/whippany rd either, but its a starting point.
https://goo.gl/maps/tVtW7SFfVPDv756M6