Seek options for your OWN well-being

I'm sorry that you're dealing with such turmoil.  You mentioned that he had a stroke, of some sort, and this can absolutely alter a person's personality to a degree that loved ones don't even "recognize" the post-stroke personality. 

You also mentioned that he's been somewhat confrontational for as long as you've known him.  Again, age, health issues, and a general malaise can contribute to a person's personality becoming "worsened" as they progress in age.  Is he taking any medications?  Is he under a doctor's care?  Is he doing anything to help himself, in any way (taking control of his health issues, etc.)?  Are you "allowed" to speak with his primary care physician as per HIPPA laws about this? 

I realize that he's got the aggression issues, but you don't have any control over this and you're making his issues into your own.  And, this is not meant to be read as criticism, blame, or anything negative, whatsoever.  Having him sign a contract might feel as if you have a bargaining tool, but do you, really?  So, if he breaks this contract, he's required to get professional help?  If he hasn't been able to control himself, to this point, what is the guarantee that a contract is going to hold any weight with him, at all?  Should professional help be viewed as a "consequence" rather than an excellent option to take as a proactive step?  What if he refuses to seek help?  What's the consequence for that?  It might be a very wise option to consider seeking individual counseling for yourself to learn how to let go of his behaviors and let him deal with the consequences. 

Yes, I completely understand and empathize with your situation - you don't want to experience an assault because of his behaviors.  There are things to consider, here, and your health and well-being is primary.  With him accompanying you during public outings, your anxiety level is increased by a factor of 10.  That's tenfold, not "ten."   Here's the equation:   Anxiety¹⁰ + Fear + Control Issues = Emotional And Physical Damage.  Stress kills, and this is a fact that medical, psychiatric, and psychological sciences are finally recognizing.  You're fearful of what he's going to say and/or do, and what the consequences are going to be.  You are feeling as if you are somehow responsible for controlling his behaviors, etc.  All of these things can be managed, but it's going to take some serious work on your part, and a behavioral "contract" is a great idea if you were dealing with a teenager.  But, you are dealing with a grown man approaching retirement age, and this "contract" simply isn't going to do any good for either of you.  He's going to resent you for introducing it, and you're going to stress about him breaking it. 

Put in a nutshell, using a behavioral "contract" is what we do with children and adolescents to teach them consequences for their actions so that they learn how to make good choices and decisions.  By the time an individual has become an adult, they are completely responsible (legally, morally, and ethically) for their own choices, decisions, and behaviors.  Legal adults break "contracts," all of the time - contracts of marriage, business contract, lease agreements, mortgage contracts..........and, so on.  He has to want to alter his behaviors for himself and on his own, and you don't have that control or power to force him into managing his own behaviors. 

I wish you the very best in this situation and I hope that you consider seeking counseling for yourself so that you can live without all of this fear and anxiety.