He could have saved himself 1.999999 billion years if he used the shovel!
Never mind the missing mountain of skulls, the missing body bones, and the practical inefficiency of burning a body to power a matter assembler (!!!!). He had a shovel... probably two of them. He could have used them to chisel at the wall far faster. He'd even get new shovels when the garden and hallways reset. He could have done it in a single lifetime, and then let himself get reset so he could exit at the age he entered. I guess none of the current writers ever played a text adventure?