OP -
Looks to me like your current 400 is probably around 53, maybe 54. I'd say your 800m repeats are too fast -- your 6 x 800m should probably be run at tempo/threshold/cruise, but it looks like you're doing them around VO2max effort. Your 8 x 400m session should probably be at *current* mile/1500m pace, but your are pushing it to more like 1200m pace. That plus no speed sessions means there is plenty of room to improve, so this is good news.
Nice work running 2:02 off that training! I wouldn't have been able to.
If you want to spend a year focusing on the 800, I'd suggest something like this - simple approach - approx 4-6 mos base training
Mon/Tue/Thu/Fri easy 45-60 min
Wed aerobic development - alternate either 5 x 1000m with 200m jog OR 20' tempo run. Look up proper tempo/threshold/cruise pace based on your 4:23 1500m.
Sat speed development - alternate either 5 x 80m hill accelerations OR 4 x 200m smooth accel on the curve then hard on the straight. 5+ min full recovery. Then plyos, drills, weights.
Sun off to recover.
Occasional 5K XC or road race to judge aerobic fitness and recalculate workout paces.
Then, transition to next phase:
Wed 20' tempo, 10+ min recovery, 4 x 150m r5 smooth accel on the curve then hard on the straight.
Sat 3 x (4 x 200m r1) r5 at *current* 800m pace, or just 1 sec faster. Over time, reduce recoveries down to 30 sec and 3 min. Occasional 800m TT to gauge fitness.
And in the last 2 months - Wed 4 x 800m @ VO2max with equal time recovery, rest 20 min, 4 x 150m
Finally, 2 weeks to taper & peak.
Just some ideas, hope this helps, good luck!