I do appreciate the time and effort you are putting in, trying to make sense of these circumstances. You are doing a great job coming up with possible explanations.
But I do have to say, with great respect for you, I feel like you are having to twist like a pretzel, to justify some of the situational aspects.
Some are surmising that Joey and family were killed, and then Chase, who has a criminal history of theft and fraud, and who has a long history of conning customers and business partners out of money, then sat down at Joey's computer and stole money from the account, backdating and deleting the evidence. The evidence of that is those checks ended up in Chases's possession, some cashed by him, and spent at various casinos in the following months. And yet, He complained that he was behind on his rent.
But the 'pretzelly' explanation is that Joey actually decided to give Chase greater access to his finances, and purposely opened up a portion of his QuickBook account, telling Chase to write himself checks as needed, and sign them himself. And then Chase would delete and backdate, because that is the way Joey set up the custom account for him, and he also expected Chase to add his own name again, so he could teach him to use Joey's accounts from now on...