AGK has the LoadFont( iFontID, szFontFile ) command which potentially you could load any font even a custom one using tier1 or tier2
without the need of any plugins. There is an extensive command set for text that will help in positioning coloring etc and if you don't have
a font that can support the mathematical symbols for example you could always use sprites which is another great advantage with AGK's
extensive command set.
If you do some searching on the forums you will see plenty of examples. but most people refrain from using particular fonts because unless
you share the font with the code there is a good chance it wont look the same on different machines.
Exporting to HTML 5 works very well and I have personally published games with no problems to html, but prefer apk files for android as that
is my main interest.
Altho it has all of the text commands needed I would personally recommend using spritesheets that have all of the alphabet/numbers/symbols
etc that you need as it can look allot nicer and they are very quick to create and will work on all platforms the same in the future without users
needing to install fonts. For this ide personally recommend a free paint tool
https://www.gimp.org/downloads/ and there is probably
people who are willing to share their sprite sheets with you
GOODLUCKfubar