Can I change the font on the Lock Screen clock on my iPad?

No.

Unlike iOS 16 on iPhones, iPadOS 16 for iPads, currently, has no Lock screen customisation features.

Sorry.

iPadOS 16.1 does not [yet] support lock screen font or widget customisation. Likewise, the active Astronomy and Weather Wallpapers are currently exclusive to iOS16.x for iPhone.

Apple do invite submission of constructive comments and feature requests via its Product Feedback portal. For iPad and iPadOS:

Feedback - iPad - Apple