What's the best training plan to break 4:40 in the 1600m?

Slow down your easy days by a little. Mpw?

Not be a weakling.

First of all i'd suggest dropping that 800m time down. One of my friends ran under 440 with a 2:08 & he was a distance runner. I run a 2:05 / 53 and never broke 5 in the 1600 which was embarrassing. Also slow down on the easy runs. Instead of doing all those 200s do about 6-8 of them at 800 pace (under 30) with about 200 recovery it might be a little tough for you but don't start too fast start pretty close to 30 then progress down. Another good workout is a 1200m time trial then all out 400 after like 3-5 min recovery maybe longer if you're tired.

Make those 400's a little bit faster. 67-70 if you can. With the 200's, do them a little bit faster to improve that 800. Slow down your easy days. They should be about 7:00-7:20. Try and drop that 800 time down a little. 2:07 sounds good. Don't do too much cross training but maybe once every like 2 weeks. Make sure you prepare well for meets. I have very similar pr's as you and just to let you know, you're better at the 3200 than anything else. That's a really solid time compared to the other pr's. Good luck.

You need some longer reps at 3200 pace. For you that looks like maybe 5x800 @ 2:35 or 4 x 1k @ 3:15. You can take plenty of rest on these.

You could also benefit from some 600s at goal pace or slightly faster. Maybe 5x600@ 1:42-1:45. Close to full recovery here too.

Im a 2:04/ 4:38 Guy and its all about staying healthy and consistent. Youre already there. My training was nearly identical to yours (minus tempos). When i broke i hadnt tempoed all year, however definitely keep up with them theyre essential for long term development. Do closer to 8-10 x 400 @69-70, split 35, 34 @ the 200. Also longer reps k's @ 5k pace and 800's @ 2 mile. One of my favorite "speed" workouts is 8 x 300 @ 800 pace.

Do strides after easy runs if you're not already. Youre already there. I ran 4:38 off 40 mpw, no need to go higher YET. Not going to see yourself drop faster from more miles, however once your times stop dropping up mileage. Good luck!