not necessarily. some will argue 2x/week is better(keeps blood levels more stable) but its really individual dependent and how fast your body metabolizes it. i personally go 2x/week and never tried once per week.
how do you feel by the 6th day? if you still feel pretty good then once per week is prolly ok for you. best thing to do is try to get bw say day after inj and then again 6th day and compare the 2. or just go to 2x/week and see how you feel. there are plenty of guys who go every 5th, 6th or 7th day and seem to be happy.
as for the acne some people get it some dont. mine is mild at trt dose. if i bump up a bit i break out pretty badly on the shopulders/upper back