I'm all for keeping the peace in ones home, with a spouse particularly. I know you and Tony have had your share of discord, and under normal (or any other) circumstances, I'm all about maintaining peace with a spouse for obvious reasons. On the Buck issue however, Tony continues to wear some serious blinders. All the while, disrespecting your feelings, needs, hurts, upsets, etc when it comes to Buck. So for that reason, I concur with the locked doors and other tips already given. I concur for laying out the "Buck Rules". And if they contrast in ANY way with rules of your home for YOUR CHILDREN? Tough Buck. Because your KIDS and grand children have no reason to necessarily have the same house rules in your home as others, including adult siblings. Not to mention, your house, your rules for any company. You do not need to explain why or how things may differ from say Cory or Buck. There is no comparison. One is your child. That's it.
I think you may have to just say "Tony, you know I love you, but we have been round and round on Buck. I've come to see that we are not necessarily going to agree on issues that I have with Buck. This is however, not your mutually exclusive home, and it is never okay to force a person to be subject to hurt, theft, ridicule and (insert list). I have made a written list of how Buck WILL conduct himself in OUR home, when and under what circumstances he is welcome to visit, and these rules will be adhered to as this is MY home as well. There will be no discussion with Buck, and I flat out refuse to continue to argue with you. You and I are a team, so if you can't actively support me in standing firm on rules in our home, I will simply state that at minimum you are not to undermine what I need to feel happy, safe, content and peaceful in our home. The list of rules and a corresponding set of consequences is written up and I plan to tape it securely to the front door, and replace it should it need replacing. I will adjust the list according to anything else that may need to be added over time. These rules aren't "guidelines". They are the letter of the law in Janet's home, backed by the law if I am forced by refusal to adhere to them to contact the law. This conversation is over, with all due respect to you Tony, because I love you first and foremost and am never allowing Buck issues to interfere and cause strife between us again".
I would then post the dang rule/consequence list to the door. I would lock house doors and car doors. Beside the rule list, I would plainly put on a separate sheet, that under no circumstances is Buck XYZ (last name) to enter without knocking and being admitted by a homeowner, even if he has been provided the house code for entry. That he is NOT permitted to use the code under any circumstances, and all entry will be considered unlawful and will result in police being called and charges laid for criminal trespassing.
I think the days of tip toeing around Buck issues, of trying to get Tony to truly see Buck for what he is, to get Tony to understand how things go missing when Buck is around etc need to just be over. He on some level must know Janet, I think he simply doesn't want to lose his brother by facing the issues and therefore having to deal with them. Well, that means it's time for the Law According To Janet to prevail. You have every right to this. I realize Tony may go off on you. If you know that in advance, have a plan to force yourself to not engage in arguing and not to be too hurt by Tony defending Buck. Retreat to your room with a activity in mind to occupy yourself and give you two some space. In the end, your sanity hangs in the wind at the whim of this complete parasite. Tony may not ever be ready to face the situation head on. You on the other hand can forcibly control your own home. Period.
I just feel it's time for you to do what you need, even if it upsets Tony. Frankly, this issue continues to cause strife with you and Tony anyhow, while remaining unresolved and a ongoing source of hurt for you. At least with this scenario, it is strife with a purpose. And at least it ends your daily Buck chronicles. (I think I would even limit days of the week he is welcome, even at Tony's request, as in work days are out, that is YOUR time with your husband, short as those couple of hours are each day).