I can answer the last part of your question by answering the first part - a possibility as to why your strength declined during calorie deficit is because your meal timing was off? As I answered earlier today - meal timing is almost as important as what you eat. Not to mention, if you do it right you will look way better haha.
Have you used Plazma consistently during a dieting phase? It alone can make a huge difference. Add perfect supplementation and diet and your strength loss should be minimized.
I honestly don't think that anyone who is a serious athlete should walk around over 10% (max 12%) body fat...over this and your body is more inclined to gain fat than muscle. At the end of the day your goal is to get stronger and not add fat, so a good base is key. If you're not a serious athlete, it is still a great benefit to you to get to a low body fat and give your body a new set point there ...after a few months at that new weight, your body recognizes that new point as normal and begins to strive to stay there. It is then easier to build muscle and strength from that point rather than adding fat.
As for your question about setting macros up - its a super individual answer depending on many factors including training intensity, current weight and body fat, body type, past dieting, past and current use of supersupplements (or lack of), activity level, stress level, sleep quality.....I'm sorry it's so hard to give a general answer. A VERY general place to begin is (for an average 200lb male in decent shape) 1.2-1.4g of protein per lb of body weight, 0.2-0.3g of fat per lb, and 1.5-3.0g of carbs per lb (carbs are the trickiest and varies the most depending on the person). I generally believe in higher carb, lower fat, medium protein distribution if the meal timing is on point and supports it. If you intelligently add carbs over time (weekly) as the body can support them, you can get to very high numbers that the body uses efficiently (I have 7-10 clients that all eat anywhere from 500-1000 carbs per day and continue to get leaner...timing and distribution is huge).