Is It Safe?
the reality about brainwalles (or any alternate method similar to them) is that they can technically be safe but there is always a very high possibility that what you created is not at all safe.
in your case, all it takes for you to lose your money is someone who is familiar with you (so that they can guess what kind of passwords you use) and try them all in a loop.
so it is best to leave the randomness to your wallet instead of trying to come up with a complicated thing yourself which may not be as random.