Hey good topic and awesome avatar. That shit makes me laugh for like ten seconds every time I see it.
I got a couple things I want to point out that I'm not sure you're noticing. The first is that your current cardio routine may not be optimal. Jarhead recommended fasted cardio. Fasted low intensity cardio ranging in duration from 20 - 60 minutes (depending on your BF) is the weapon of choice in body composition alteration. Bodybuilders have been cutting fat and gaining muscle simultaneously while implementing low intensity cardio, usually in a fasted state, since the 60s. High Intensity Interval Training (HIIT) has some solid research that it may be even more beneficial than low intensity, but the majority of the best BBs in the world choose to do low intensity still. Mostly because it works. You said that your cardio routine is a high intensity boxing session 2-3 times a week. Such cardio may be intense, leave you winded and make you sweat like a pig, but when your heart rate gets past a certain threshold (about 160 bpm for your age and BF) you're not burning fat efficiently. The cardio is so intense that you start to burn muscle once your glucose is depleted. Given that your not taking in a lot of carbs, it won't take long for your body to start pulling from muscle cells to fuel the boxing. Keeping the intensity lower (about 120-130 bpm for you) and maintaining that heart rate for 45 - 60 minutes a day 3-5 days a week will be the optimal fat burning/muscle sparing cardio protocol if body composition is your main goal. Doing it on an empty stomach ensures that you're not spending the first 40 minutes of cardio burning through the meal you ate before you got to the gym, but rather attacking the fat stores immediately as your blood sugar will be at its lowest levels of the day.
Furthermore, I'd like to see you try carb cycling as well as a more keto based diet. It sounds to me like you haven't put a lot of healthy fats into your diet as you've never mentioned them. A higher fat intake along with lowered carb intake will adapt your body into utilizing fat as fuel which will then train your metabolism to burn fat more efficiently, even while at rest. The key here is to experiment with your macros. Find what works and what doesn't work. Don't be overly concerned with the calories, but be concerned with the macros. Play with those numbers. All in all, Jarhead's advice of implementing fasted cardio, especially at the highest range of 60 minutes a day, will drastically affect your fat loss.
I find that the best results come from focusing on one thing at a time; e.g. if you want a bigger bench press, having a secondary goal of losing bodyfat will slow your bench press progress. Dividing your time and focus spreads your effort out and minimizes its effectiveness. If body composition is your goal then putting the boxing gloves down until you get where you want to be will fast track your progress. You can still have multiple goals at once or enjoy multiple disciplines, hobbies, etc, but understand your progress is likely to be slowed down.
