Pull battery, reinsert, press and hold (in this order) vol (+), physical home button, then power. Hold all 3 until screen blinks a couple times, let off of power button but continue to hold vol (+) and Home. If you have a custom recovery, this should get you there.......
Problem being, if like u said in op you also flashed a boot logo(splash screen)different than boot animation - the boot logo is earlier in the boot process than recovery and when it gets corrupted, recovery options don't apply because the device won't be able to access it since the boot process is corrupted before the recovery
If it was ONLY a font that got you here, then you WILL be able to access recovery. Fonts are flashed to the /system partition, and if there in a problem , /system is the final step in the boot process and CANNOT NO-WAY cause ANY harm early enough in the boot process to prevent you from accessing recovery. So give it a try.
---------- Post added at 06:34 AM ---------- Previous post was at 06:21 AM ----------
The pic shows ROM toolbox font installer- highlighted is the default location for flashing the fonts
Below is root explorer showing the s3 filesystem fonts are in the correct directory as set as default for ROM toolbox.
So like I was saying, if it was just a font this is a very simple fix for you. Boot into recovery, flash a ROM which formats and writes /system, fixing any kind of error that installing a font could have caused