This won't let you change the spacing of the clock or from a 12h to a 24h clock, so you have to create a theme using the format you want first, and then we can change the font from there. I'm not totally sure if you need root for this or not, my phone is rooted and I was using root browser to get to the files.
First, get your theme set up how you'd like it, besides the font that is. The first picture attached is an example of my first font swap theme before I did the swap.
Second, find the two fonts that you want to use and download them.
Next, navigate to sdcard/Android/data/com.omnitel.appcessory.gear.watchstyler.manager/theme/(what you named the theme we're editing)/texts/fonts. See what the font files in this folder are named, and rename the fonts you just downloaded to the corresponding font you want to change. For example, the clock font in the first image is named debussy.ttf, and the one I replaced it with is named varsity.ttf, but i renamed it to debussy.ttf so the app would see the same file name and substitute that font file for the one it originally uses. Same thing for the date font.
Last, move those different font files you want for the clock and date to the fonts folder we were looking at before, replacing the font files that were originally there. They should show up fine now, like they do in the second picture I've attached. Note that your preview in the app will not change, and I haven't messed with trying to get it to update, although I imagine it might update if you delete the PRV_IMG.png in your theme's folder.
If anyone has any questions or wants more pictures I will answer whenever I can, it should be pretty self explanatory though.