WW still contacting OM although she doesn't know that I've checked the cell phone records. I've opened up a separate bank account so I'm tempted to deposit the required amount and start direct depositing my paycheck into my private account and then write WW a check to cover groceries and such for our DD's.
I think this is ALWAYS wise when a spouse is wayward. They can wipe out a family's joint assets pretty quickly, if they set their mind to it, and right now her mind's a mess, and it categorically does NOT have your marriage's best interests at heart if she's still in contact with OM.
If you do this, TELL her once you've done it (not before). Be confident, and tell her "I feel this is best, considering where we are right now." Do not apologize for it, nor be angry or accusatory -- just matter-of-fact. Don't pay for ANYTHING that enables her affair or waywardness (cellphone, hair coloring, make-up, cosmetic surgery, gifts for OM, etc.). DO pay for her legitimate needs (insurance, food, shelter [but not her own place]), and err on the side of being generous when in doubt.