Senior Friend Made Me Joint Account Owner With Ros, Passed Away, Hesitant To Do Anything With The Account Due To One Of His Children

General advice of course:

Location: Indiana United States

Was made a joint account owner with ROS of a close senior friend about a year ago. We've been close for around 8 years where I've done almost everything for him, daily, for the last 4 years other than the last year he was in a nursing home. I've journaled our visits throughout the last couple years regarding how he is doing and his health since I help him with meds, doc appts, grocery, bills, etc. For bills and payments, I never used the account for any of my needs or payments. I set up his bills on autopay to directly come out of his account so that I wouldn't have to be involved as much. For groceries and other random expenses, I'd just pay them with my money, document, and reimburse myself the cost from the joint account, typically at the end of the month.

We met around 4 months after his wife passed away and he has had no one to help him (he is limited to a motorized scooter). He had an estranged child (blocked his number, haven't talked in over 10 years) and would often go back and fourth, most times saying he is not leaving them anything at all to sometimes leaving them between $500-1000. There was never a will left. So I assume they will be inheriting the house (it's considered not safe to go back to and one of the reasons he had to be moved into a nursing home, no other cars or assets).

Originally, we both assumed he would go to the rehabilitation nursing home, get better over a few months, then come back home as this happened a few times in the past. While overall health was fairly stable (80s, a few chronic conditions, immobile), the nursing home eventually considered him not a safe discharge and that I'd be liable and responsible if I took him home and organized in-home nursing for him. In the meantime, while I was helping arrange his house for him to come home, I had to remove his bed to change it to a medical, reclining bed and mattress. He's told me throughout the years about where he keeps his money and was transparent with me about it and that I was the only one who knew. However, I had no clue how much he had, given the way he lived and never wanted to spend any money, which now kinda makes sense how he'd rarely spend throughout his life and only saved. There was around 50k in the joint account when he added me.

So we talked about depositing the money into the account since no one was going to be at the house, possibly selling it, and payments were starting for the nursing home since he was not on Medicaid. I contacted the bank ahead of time to let them know the situation and then I deposited it (over 500k). We remained close until he passed away around 8 months later in the nursing home. There remained no contact with any family just me and another friend from church we had in common that would visit from time to time until he passed away around a month ago.

I understand joint owner with ROS that the money is legally mine and that he wanted the left over amount to go to me. However, I feel timid in using any of it at all since I'm not sure if one day down the road during probate or that I could be sued by the child somehow? When they are Executor can they look into our joint account and if they see the money and pursue it?

Looking for a worse case scenario or how I could of protected myself or still can? Should I have spent and deposited money in and used it more so it wasn't considered a convenient account to just help him? How long do I wait to even do anything with the account?