nice that you have a training partner for the intensity stuff. For the 400s what intensity were you running. your HR monitor isn't very conclusive for short intervals. What was your intention? I kind of feel like you were halfway between these two:
You can do 400s as z4 which is like 3000-5k race pace with equal or less recovery OR
you can do 400s as z5 which is very hard with major lactate accumulation and requires 2x or even 3x recovery.