After reading RR's play situations, this is how the play clock stuff boiled down in my simple mind. Happy to have others poke holes if there is any flawed logic or conclusion:
Anytime there is a B helmet off or a B injury, in combination with a foul, helmet off, or injury by A or B, the play clock will be set to 40. If the only thing is a B helmet off, under a minute, the play clock is 25.