I know the struggle when you're dieting down and still trying to keep your strength gains. Pushing too hard is how injuries happen, so what's worked well for me during this cutting phase is to keep my rep ranges low, and focus on explosiveness and power. I think you're right on with your rep range, and the important thing is that you're keeping your CNS activated to maintain your strength levels, and with proper diet you won't lose too much of the good body mass you want to keep.
Once you're in a position where you'll be maintaining your body weight, or going back to a bulk, you could potentially look at that 405 squat goal. I'm of the opinion that with the right programming and nutrition, an experienced strength athlete should achieve a 4 plate squat. Smolov Jr is an accessible program that helped me get to 405 and beyond. Bulgarian Method is another program that works very well, but it requires a home gym and the ability to train multiple times a day. Westside Barbell uses many of the principles found in the Eastern European training models, and has been successfully modified to fit the lifestyles of most lifters who have jobs and families and can't train all day, everyday.