Switching themes from custom.html

I've got my interface.html file somewhat set up now and it works decent for sending the settings (still have to hold the button for 3 sec to reset the watch), but I could not figure out how to get the values from an existing shadowclk.json file on the watch to be used for the preview.

I'm sure there are a number of ways it could be better and I'm open to all suggestions. If anyone knows how I can set the preview to show what's in the watch settings already, please let me know. Thanks. I did use some AI assistance with the coding since I'm still very new to programming and trying to learn as I go so there may be some glaringly obvious issues that I don't see.

You can try it from here.