After a good bit of work, I finally have the simpler bootloader working. It's a total of 370 bytes - a far cry from some of the very simple bootloaders for like the Altair 8800. I decided to write the first program I got working to RAM since it was small and simple. It does a quick 35-3 and writes the result to the UART, so repeats the character "2" over and over. The program is 12 bytes, so requires 12 write commands, and the the jump command. I put the program at 0x9000 since nothing else is there.
I also continue to uncover bugs in the VHDL, so it's not just a software effort. I've also started ordering some parts for the solderless breadboard version to start building. At the same time I've been looking into assemblers from previous suggestions and even looking into doing one from scratch. It will be super slow trying to convert assembler to machine code by hand to enter into the bootloader, so I'll need something for sure.