I am very sorry to learn of this situation (your child's disability and your financial struggles surrounding it).
Unfortunately, your failure to listen to your attorney's instruction, and your spending on your child's funds are not going to be very helpful to you and the upcoming hearing is probably not going to be very pleasant.
The court is going to want to know why you spent the money that came from the personal injury settlement (funds that are designed to ensure your child is positioned in as close to a financially secure place as possible), were used for things such as a very expensive vehicle, a long vacation, purchasing gifts, etc.
Your financial hardships cannot be compensated by your child's financial award (so the child's award cannot be used to pay off your debts, or otherwise cover your expenses).
You can defend these purchases if they were for example: a wheelchair van (an expensive vehicle, but required for transporting a wheelchair bound conservatee); vacation expenses - but only if you paid for only his vacation expenses and kept your own (or whoever else went) separately and paid for them as such - his funds should not be used to pay for others to go on vacation; gifts are not a legitimate use of these funds.
I cannot tell you what the outcome of this hearing will be - I am not sure what exactly led to your dispute with your prior attorney that led to them dissolving the attorney/client relationship or if this was ever brought to the court's attention/notice; prior instances of misuse of the conservatee's funds are certainly going to be an issue.