it seems like a good-enough of a solution. I cant figure out how to add a metal resistor on the xschem side though. There does not appear to be a schematic symbol for it.

Because the model name is a property, you can instantiate, for example, a

sky130_fd_pr__res_generic_po

and then change the model name from

po

to

m1

(or whatever) by editing the instance.

I tried that and it seems that xschem generates a "multi" parameter which is not in the metal resistor models and that causes issues with ngspice. Is there some way around this?

Use this.