The workout sample I gave is exactly what I would want for someone of your abilities to do. You are maxed out at the time you can run a 400m in according to your PRs.
Decrease the amount of work you are doing and raise the intensities. 35s special endurance runs should put you at about 280-290m, so go from start line in a lane to the start of the final 4×1 exchange zone when doing the special endurance runs. Add a second every 3 weeks to that workout and you should be around 325m by the end of fifteen weeks @ 40s which would give you a decent chance to break 50s in the 400m and I bet you can do a 350TT in 43-45s depending on fatigue and motivation at that time as well.
You’ll have to find alternates to some these, but save the speed endurance till 9-12 weeks from now.