Am I thinking about interest correctly?

I owe $214K (ouch) total (interest + principal) from law school (all Grad PLUS). I have 148 qualifying payments. Based on my current payment ($684.14) per month, my loans "grow" by around $400 per month. This is because interest is $1080 per month at 7.5%. Though oddly, over the past few months the amount seems to vary by 1-2 hundred.

Am I correct in calculating that based on my current payment, with 152 payments remaining (Old IBR requires 300), my final loan balance will be $60800 higher (400 x 152) and my forgiveness amount will be around $270K? In reality it will probably be lower as my income will increase over the next 12 years. I already know my payment will increase to $729 when I recertify based on our AGI from our 2025 taxes.

Does interest work this way? As long as I do not leave IBR, it will never capitalize?