I look at it differently. Your 135 is probably like other people squatting 225 or 250 because of the extra body weight . But yeah, you should definitely drop about ... oh 140 or 150 lbs.
My experience with doing 3x3 instead of 3x5 was that i improved for a little while and then started going backwards. Moving back to 5s was a pain too. For me 3s just doesn't seem to be enough "endurance" work.