Need help with customization of badly written premium theme

Hi, I've bought a premium theme Tripod at ThemeForest and is extremely badly written, no Child-Theme support, everything done with classes which are awfully long and not make by functions or other useful things at all.

I need to do some customizations, simple ones, but they have turned to be really nuts, could anybody help me?

a) add key support at gallery (here: )
The template uses Galleria Folio Theme.
And I've found that there should be API to do this, but I have no clue, how to add it into theme:
You should be able to use the Galleria API:

Galleria.ready(function() {
        left: this.prev

b) get rid of theme lightbox (I know, how to turn it of, but I haven't found a way how to add some fullscreen lightbox instead of it, I've found this one but I haven't succeded to manage it in post.class.php or fix the jquery which is called on it, could anybody help?

post.class.php -
functions.js -

I feel really bad, I've spent 60 dollars, my client wants his site and the theme is simply so crap (I should have first get one on black market to see the structure).