WigglyPaint can't do that out of the box, but it's possible with some minor tweaks!
If you switch to the "Widgets" tool and double-click on the invisible button over the "Export" floppy disk in the bottom left corner (it is currently named "button1"), you can click the "Script..." button in its properties panel to view the script that handles GIF exports. Currently it should look something like this:
on click do play["snap"] t:if options.widgets.mask.value () else 0 dict 32 end gif.frames:target.frames..copy[].map[t] gif.delays:3 take 10 write[gif] end
Replace it with the following:
on click do play["snap"] t:if options.widgets.mask.value () else 0 dict 32 end o:image[card.size] each w in (target.index+1) drop card.widgets o.paste[app.render[w] w.pos] end o:o.copy[target.pos target.size] gif.frames:target.frames..copy[].map[t].paste[o 0,0 1] gif.delays:3 take 10 write[gif] end
This updated script finds all the widgets on the card which are above the WigglyPaint drawing canvas (it is currently named "target"), draws them without the card background, and then overlays that drawing on each frame of the GIF.
When you make customizations like this I recommend saving a local copy of WigglyPaint so you don't have to perform this modification every time. Everything about Wigglypaint can be improved to suit your preferences!
You can change a field widget's font by selecting it with the "Widgets" tool active and choosing "Font..." from the main "Widgets" menu. By default, WigglyPaint only includes Decker's three built-in fonts, but you can install more: see the "All About Fonts" deck which comes in Decker's "examples" directory for more fonts, more information about fonts, and a font editor. You can also download a copy from here:
https://beyondloom.com/decker/fonts.html
Does that work for you?