>make them like lv4.5 with a bonus to their rolls
How come I did not think of this ? This is a really great idea. I am definitely going to use this. And modify my program and test that solution and make more stat charts.
>I downloaded a free dice roller on my phone to use
About that, this one is really nice. You can have several tables to roll the dice (so you don't need to reconfigure every time you switch LVLs). It does not allow you to add a bonus to the dice result though. Which one do you use ?