Hi, I’ll try to help out. I’m also new in this whole GD modding shenanigans…
So, the changes you want are super easy to do.
Get into Asset Manager, go look for squall01.dbr at records\skills\playerclass06.
Open and you should see (on your left) all the different groups that skill has. Spawn Config should be the 2nd from the top. Go in there and set petLimit to 5, instead of 3 and spawnObjectsTimeToLive to 30, instead of 12.
Done, just build the mod (usually pressing F7 or choosing Build on the top bar).
Also, this is me guessing, your error might be because your game files weren’t properly extracted? Check this out: [Script][Basics]Modding Beginner's Guide I
Maybe you don’t have it setup properly. Also, try to run Asset Manager with Admin Privileges (right click it and choose run with Admin Privileges.
Anything else, I’m still a noob too 
Hope it helps 