Re:Methods of Progression
Warm up with lower weights and push for a greater leap ie 120 130 140 then 145 etc. After four sets at 140 you are more tired, don't make the run in so long!
Try some stop / start sets, ie 145 one rep rest, repeat until you have done 5/8 so in fact you have done 145 for 5 or 8 but you rested between reps, then as you get better, cut the rest time until you are doing 145 for 5 straight!
Get some help stopping and allow yourself to practice power reps pushing up hard and help down then try the reverse, help up and focus on the negatives. Doing both will improve your handling and confidence at that weight.
Hope that helps.