I want to destroy the Brotherhood with the Railroad and then destroy the Railroad for the Institute.


I completed completing powering up for the institute - then end of the line started - but i did not speak to father. Instead I talked to Z1-14 and saved the railroad.


Now Rocket's Red Glare activated but I still have the option to talk to father.


If I complete Rocket's Red Glare will the Institue become hostile? Where's the point of no return?

It doesn't matter who you destroy the BoS with. Father would just skip over destroying the BoS if you have already done it with the RR. Once the BoS is destroy, the RR will start to destroy the Institute. While the Institute will order you to destroy the RR, both are the point of no return for both groups.

So can I turn in Rocket's Red Glare to Des to get the achievement or will that automatically lock out Nuclear Family?

Yes, you can. It would skip straight to Nuclear Family once you finish off the Railroad.