I think the LBS taking a good hard look at themselves and how they may have contributed to the breakdown of their M is wise.

To me, the only controversial piece of your post is writing W a letter. Actions speak louder than words. I would skip the writing and just do.

M: 42
H: 43
M: 8 years
S7 and D4
H has D19 and S25 from previous M
Bomb: 3/6/14 OW discovered, EA & PA
1st separation, 10 days, decided to reconcile & moved back in. Fail
2nd separation: 5/1/14