Firstly, good luck with continuing your prep and your show man! @The_Mighty_Stu coached me as well this year for my first two natural bodybuilding shows, hell of a guy! Here's my .02:
Not at all, once per week body part splits are the staple of bodybuilding! Once per week body part splits are the gold standard for bodybuilding, because they work. Check out these articles for some great info on designing a great Bodybuilding program by Clay Hyght. Part 1, part 2.
Now, this is not to say you can't make gains on 2x per week. For example, right now I just started a plan training twice a day, hitting every muscle twice a week. But, I'm going to do 2 weeks on, 1 week off and see how that goes. I recently have been hitting shoulders and arms twice a week for 5 weeks, then the past 2 weeks back to once per week for some recovery. Ultimately I'll go back to a 5 or 6 day split for my next prep as I did for my shows, and for the past few years. I think @BrickHead mentioned that varying up a little bit every now and then is good and should be done smartly, but the once per week body part split should be your foundation, your backbone IMO.
Remember the point of training is to RECOVER from training. So, more isn't always better. If you're hitting once per week, you can really go after it and destroy the workout, get some drop sets in, or forced reps, and enjoy a week of recovery for that muscle. Also keep in mind certain muscles are worked regularly in some manner. When you work chest, triceps are getting some action. Same with back and biceps.
I think there's merit to once per week, twice per week, etc., but twice per week does run the risk of overworking the muscle and not getting enough recovery if you're not careful.
It seems like you may be overthinking this a little bit. As @BrickHead has already mentioned, bodybuilders do split routines. Natty or assisted, it works. Higher frequency has it's place at times, for in terms of longevity and consistency, you just can't go wrong with a standard split routine.
Again, higher frequency (hitting the muscle more than once per week or training twice per day) DOES NOT NECESSARILY mean you'll make more progress, and it's possible you may be overworking/under-recovering. I would very, very highly recommend designing a standard split routine. It doesn't need to be a "hurdle", just design the program and start it. Use the Clay Hyght articles as a template, easy to plug in some exercises and get started. I used that program for a year and a half before making some tweaks.
Regarding your BF levels, I wouldn't stress about it or use the calipers or whatever, it's irrelevant IMO. Look in the mirror, take pics and go from there. The judges don't care about your BF percentage, just how you look.
Definitely focus on lats and delts, you want that nice V-Taper. Also if you're not working calves directly, definitely do! Twice a week is good, I usually do them at the end of the workout. 4 sets standing calv press followed by 4 sets seated (or vice versa.)
Good luck, keep us posted!