There is nothing wrong with the way you use the SIG Pro plugin, but I was just curious of why you didn't use the K2 gallery.
I strongly believe that whatever method you choose (K2 gallery or the SIG Pro gallery) it will be the one that suits you best.
Read below a small description on what is the K2 gallery and how it works.
The K2 as a component has the ability to connect to each article a gallery by going to the appropriate tab (When you create an item you have available the following tabs: Content, Image, Image Gallery, Video, Extra Fields, Attachments).
The K2 gallery needs the SIG Pro to work though, that's why we suggest having it as an installed plugin.
It takes the parameters you have set inside the SIG Pro plugin except the path which in K2 is different (it's in media/k2/galleries) and you don't have to add it to the parameters it's like a default path for the K2 gallery.
Now you will probably ask me how does it work so I'm telling you this: you create a zip file with all your images and you upload it inside each items gallery tab. The path to go and find them is the one I have mentioned above.
I hope I didn't confuse you even more ???
If you have any other question I'd be glad to help :)