Lots of good stuff already posted in here, not too much to add.
The one thing that I wouldmention is frequency. In trying to acquire a new skill, I don't think 3x per week is enough, not really. You'll go one day, then you've forgotten much of what you've gained by the time you get in the water the next practice. By going 5x per week, even if they are shorter sessions, you are regressing less after each session. I always feel like if I miss practices, the first day back is a bit of a write off. The second and third day in a row is where the improvements start to come. So even if you do only have time for 3x per week, if you can schedule them on consecutive days then that may be beneficial.
The other important thing is to pick one thing at a time to work on. Pretty sure that was already mentioned. Work with your coach to get that going.
Finally, you aren't starting from a terrible place. You aren't fast, but you are ahead of a lot of other people your age. You've improved by about 10s per 100 over the last 16 months on a relatively minimal time investment. If I told you that you'd improve your run speed by 40s per mile on 3 hours training per week, I suspect you'd be ok with that. This is pretty much the same thing.
Swimming Workout of the Day:
Favourite Swim Sets:
2020 National Masters Champion - M50-54 - 50m Butterfly
The one thing that I wouldmention is frequency. In trying to acquire a new skill, I don't think 3x per week is enough, not really. You'll go one day, then you've forgotten much of what you've gained by the time you get in the water the next practice. By going 5x per week, even if they are shorter sessions, you are regressing less after each session. I always feel like if I miss practices, the first day back is a bit of a write off. The second and third day in a row is where the improvements start to come. So even if you do only have time for 3x per week, if you can schedule them on consecutive days then that may be beneficial.
The other important thing is to pick one thing at a time to work on. Pretty sure that was already mentioned. Work with your coach to get that going.
Finally, you aren't starting from a terrible place. You aren't fast, but you are ahead of a lot of other people your age. You've improved by about 10s per 100 over the last 16 months on a relatively minimal time investment. If I told you that you'd improve your run speed by 40s per mile on 3 hours training per week, I suspect you'd be ok with that. This is pretty much the same thing.
Swimming Workout of the Day:
Favourite Swim Sets:
2020 National Masters Champion - M50-54 - 50m Butterfly