My father is considering divorcing his wife. He and my mother bought a house and business years before she died, and we have kept careful records showing my stepmother has never contributed to either (all household bills have been paid for using his retirement income and Social Security; she's never worked, rents out her house and her social security seems to go to her children). They have not lived as a couple for years, pretty much living completely separate lives (she doesn't cook for him, does no cleaning in the rooms he lives in, etc)
The one thing holding him back is he doesn't want to lose half of the house and business (which he owns on paper and I run for him) or his military retirement. It's my understanding he wouldn't, as he owned them before marriage and she's never contributed to them (he had been out of the military for years before they married); am I correct? He changed his will about 8 years ago leaving everything he owns to me, and his health is still very good, so there's no question of senility (except for putting up with her for so long

)
Any advice I can give him?