(1) decent crypto is just plain cheap; and: does an LFSR _have_ a middle? (if all bits were shifted 17 bits around, it would be just as good an LFSR)
I don’t know how to think about pseudo-random (it is supposed to look random, unless you play “unfairly”); I do know how to think about crypto: if the key is secret, distinguishing the output from random is _VERY_ expensive.
(2) without randomized rounding, 1+0.1+0.1+0.1+0.1 …. (all the way across 100 pages; rounded to integer) will still be 1. Randomized, it will be 0.1*(# of adds), +- epsilon.