hi i have not direct experience with this but some ideas, sure you know them, but may encourage you. if anyone else out there has more experience please let us know

feel surgery correct in not being option as will not hold, therefore rehab only way to go. longitudinal tear would seem much more favourable than horizontal eh, so agree may well go fairly quickly up the rehab ladder.

would think treat like any other strain you have come across and use milestone approach. acute management, RICE and MEAT. gentle stretching, lots of massage to break up scar tissue and encourage good healing. strengthening, isometric, isotonic, eccentric, isokinetic. lots of CV work on bike, swim, aquajog, walk in water etc. it wil go as fast as it goes, everyone is different, by following good gradual pathway you should encourage efficient and safe rehab. core and technique education.
good luck