I'm not against the idea of people writing their own agreement, especially when it's a short term marriage and there are no kids, but the facts you're giving are a perfect example of why saving a buck during a divorce can backfire -- "penny wise, pound foolish." Having an attorney go over an agreement and make sure it doesn't contain potentially explosive ambiguities isn't expensive - it can be literally just a couple hundred bucks (if the two of you are waiving discovery and only having an attorney review the agreement for clarity and are willing to sign a "limited representation" retainer agreement to this effect).
I'd need to see the agreement they wrote to really answer, but based on the basic law, you're correct. If they distributed the business and she has a set entitlement to be paid when the house sells and there's a support component that he's paying (was the support properly worded - did it address Crews and the marital lifestyle issue?) then I don't see an argument that she's additionally entitled to income, especially if he's the sole shareholder... But again, it could come down to the wording of the agreement. If she files a motion and it's not clear, the court will probably order a hearing, which will end up costing far more than having the agreement drafted properly would have cost.