2. after looking at this again I was incorrect on what is happening. In version 9.1.60 when you mined a block you would have 4 transactions. The first transaction was labeled "mined" with the pickaxe and the amount of the block (currently 45). The second transaction was a "deposit" for the block. The third transaction was a "deposit" from my prepared deposit. The fourth transaction was labeled "deposit change" with any overage from my prepared deposit coming back to me. In 9.1.74 I am no longer getting that first transaction labeled "mined" with the pickaxe and the value of the block mined.
I must say that you have a firm grip on how the system works, I'm impressed!
Just one small correction to make things maybe even more clear:
The deposit change can only come from the deposit tx that the system creates by itself, and that deposit tx is only created to spend the reward. The deposit txs that you prepare manually yourself can never be modified, and hence can not have a deposit change. As mentioned, just a minor clarification.
However... I'm working on having the software automatically prepare deposits from everything that is available in a wallet to simplify the mining process. That way a miner could just start the miner, set some parameters, and watch the wallet content go into deposit block by block. I didn't want to enable this before, since software automated access to a wallet always poses a risk. But I think the time is right to introduce it now, with a switch to be able to disable it.