Felix, glad you're feeling better.  Chiropractic treatment is safe.  The modalities described are quite relaxing.  The knot your wife is feeling is muscle guarding and massage will help it relax.

Ice is very safe.  To actually  cause nerve damage you'd have to ice for hours.  You can get frost bite if you ice directly on the skin.  But if you rub some vasoline on the skin first, place a damp towel on the skin, ice and then several dry towels, you'll be safe.  It takes about 20-30 minutes to get maximum benefit from ice and it can be uncomfortable until the superficial nerves numb.  The reason cold packs are used more frequently in hospitals is for their convenience.  They are no more effective than ice.

Felix, Your back pain is probably caused by a trigger point (muscle spasme around a nerve).  stretching it the first line therapy.  But you have to do it right - slowly, holding a slightly uncomfortable stretch for a minute or two until the muscles relax and then stretch it out a little farther, etc., etc., and NO BOUNCING, that could make it worse.

The most common cause of lower back pain is tight hamstrings and hip flexors.  Try sitting on the floor with your back against the wall and stretch your hamstrings.  Then, sit on a chair and cross one ankle over the other thigh with the crossed leg parallel to the floor and slowly bend forward at the waist.  The stretch you feel in your butt is your hip flexor.  Then the other leg.  In addition you can stretch your calves and groin.

Ratamatatt