Sorry for all the questions but:

Can Dravis spend his focus whenever he wants, or does it have to be when attacking/defending?

@Rogue_Group1 listen to what they say.

Attacking, defending, or by using some other upgrade that requires a focus to be spent.

You cannot freely spend things. Ever.

You can only spend them when some game element gives you an opportunity. Typically this would be attacking or defending (note that you can spend a token even if you rolled no eyeballs) but others include, for instance, flipping Intensity, regenning with R5P9, etc.