I'm assuming you're referring to the FSMC on the STM32? You might want to be explicit regarding what microcontroller you're referring to.
You're correct in noting the speed difference with the HD44780 - it is dog slow by today's standards. Therefore it is probably not a good idea to do this. I'd suggest using standard GPIO and running the HD44780 in 4 bit write only mode. This requires only D4..7, E and RS. 6 GPIO. Even then, you need to ensure your code does not do things too fast.
I've not got experience with the FSMC, but it would need to be able to be setup to work at the 1MHz speed of the HD44780 and then changed back to get reasonable speed with the sram.
What would the address be? Depends on how you've wired it. If you're sharing with sram, you'll need some logic to select one or the other. This will determine the address.
Whilst it is educational for exploring the possibility, it is probably not a good idea. Use GPIO and move on.