Deciding

I've got a marathon in a little less than 3 weeks, and I've got a few nagging aches and pains I want to have gone by one week out. I run every other day, cross train on non-running days, and take one day off before my long run I intend to keep this until about the last 10 days, wherein I will begin taking more rest days.
I need to eradicate a stiff lower back, and a strong pain in my inner left groin area.
Stretching 3 x per day under physical therapist advisement.
To expedite healing, should I take complete rest days, like 3 or 4 in a row, to get rid of these pains, or can I cross train? I'm not sure which would heal me faster.

STATS:
Sleep: 7.2 hours
Run: 7 miles @ 7:46 pace
HeartRate:156
Cool and crisp, but blasted groin and back were tight.
Recovery Window: +34mins