If you elect the 4% SF nonelective up to the last day of the following plan year, you are a SF for the year. So if that is the only employer contribution you are deemed not top-heavy.
Though you would need to make it to all eligible (though I believe you can exclude HCEs still), not just the deferring because you can't add a retroactive SF match.
You need way more help than you can get from this board for free. There are people on this board who are qualified to help you but it won't be cheap. Your problem is fraught with all kinds of legal issues.
I know that isn't answer you wanted but it really is the best answers. Unfortunately, the people who helped you in the past didn't warn you about issues like this long ago. You can literally search real estate in plans on this board and you will find threat after thread of people having this and other problems of putting this kind of asset class in a plan like this.
I feel for your problem but it won't be cheap nor easy to get a fix.
Interesting. Thinking about Berkshire Hathaway and all it's wholly owned subsidiaries. I'm sure they have teams of attorneys, internal and external, who are experts at the control group, affiliated service group, and QSLOB rules. Guess I shouldn't complain when a colleague asks me to opine on a control group question!