@M3th0D I was getting 15khz out of HDMI like you but i went into a hdmi to component converter, using retropie.. I came a cross this post when i was trying to work things out, and seen the runcommand , I used it but in a different way,,I got emulation station running in 480i, and retroarch running in 1600x240.. and it switches back to 480i when exiting games.
https://retropie.org.uk/forum/topic/22467/hdmi-to-component-crt-help-runcommand/10
just wanted to pass on the info.