1 & 2) Think of AeT heart rates as an upper limit. Trying to train right at them will end up with a lot of time above. Target an average intensity of 5-10 bpm below.
Racing: Does the plan have any intensity built into it? You could substitute the races for those intensity days.
When it can fit within a training plan, I think it’s wise to race for “research purposes”. Racing is an art unto itself, and it’s a common mistake to avoid it while training. That might work if someone has raced a lot, but the more educational racing you get, the better. For these “educational” races, ignore your results and focus on what you can learn from the experience (pacing, pain tolerance, psychology, etc)