The OP's friend just has to bite the bullet and get divorced. Rip off the bandaid. Otherwise, this kind of stuff is just going to keep happening to him over and over in different contexts for the rest of his life.
1. Friend owns real estate where title is held in his name solely and needs to sell? Well, wife has to sign the deed to convey over her marital rights (her equitable rights even though he has legal title) for title defect purposes. Guess how annoying that will be when he's signed the purchase agreement and is 7 days away from closing? Wife may try to exact something out of him in that moment for her signature.
2. Friend dies owning property with a Will leaving it to some kids or other third parties (say new girlfriend)? Sorry, wife has an "elective share" right to take against the Will and is obligated to receive notice of probate (or non-probate for that matter) proceedings so she can decide whether to exercise her rights to mess up his estate plan and take some of his assets.
3. Friend wants to change beneficiary designations on his 401(k) account from an employer-sponsored plan and name his children now the beneficiaries instead of estranged wife? Sorry, wife has to sign a spousal consent waiver first before the change is effective.
4. I can go on and on with all the potential problems for friend that can arise that wouldn't arise if he was single.
Count me in the camp that thinks the buddy made a horrible decision to buy real estate during marriage with an estranged spouse unless he wanted spouse to also be involved, have rights to the property, etc. Family law and property rights law in Iowa is fairly settled law and doesn't change much. Buddy just needs to make better decisions and get a divorce (or legal separation, I suppose, but if you're going to put in that much time and effort into legal proceedings might as well sever all ties) so that he can move on with his life.