I would say what you are after, a guarantee of getting the money back from him, is not something that is really achievable. He does not have the money to repay you and is, for all intents and purposes, a thief.
The best you can do in this situation is to get it set in stone that he owes you the money. There are two ways you can do it.
The first, and the one with the most likelihood of success, is to report him to the police and request an order of restitution from the prosecuting attorney. This will require him to pay you back or face further criminal
sanctions, which will be added to the criminal sanctions which may already be laid against him by the State.
The second way is to sue him for fraud and obtain a judgment. Because you are talking about him owing you more than $20K, this is a case you will have to file in the district court
or county court. This will generally require an attorney. However, you are likely to get a default judgment against him, so the attorney's fees should not be that much (a few thousand at most, but probably under 1,000).
Obtaining a judgment against him gives you the personal right to seize his belongings and his bank accounts. You won't be able to get his benefits paid directly to you, but you can seize them once they are in his bank account. If he has any property that is not exempt, you can also seize that. This requires a lot of work and diligence on your part.
I recommend the criminal prosecution path. It has a higher likelihood of success and a lesser cost to you personally.