Protein powder conundrum

Absolutely - the basal starts taking affect AFTER you have taken it so if you reduce it on training days, it will mean you have less for recovery days.
(Sorry, for the change in terminology from "non-training days" to "recovery days". It helps me think about my body recovering from the liver dump on the training day.)

 

That is why I suggested you may want to increase your basal for your training days (increase it at 9pm the day before).
If this would result in night time hypos, my only other suggestion would be to do a correction bolus at 4pm - you know approximately when it happens and, I assume the level is consistent, so you may even be able to proactively bolus 30 minutes prior.

Long acting insulin which is used as basal on MDI, assumes our body needs a constant level of insulin all day.
Unfortunately, this is rarely the case: for example, many people need more in the morning to manage dawn phenomenon and it is common to need more when doing cardio exercise and less when doing resistance training. Through injections, we have little scope to change the basal levels on less than a daily basis.
This is where an insulin pump becomes valuable. A pump works by dripping fast acting insulin at all times of the day as the basal. Therefore, we can adjust the rate of basal at different times or temporarily when you do exercise.