i'm also new to this powerlifting game, but i'm very lucky in that the guys i train with compete at world level (2 of them are champs) and i had a similair problem getting the 100kg bench (225lbs). having not yet looked at this 9 week programme mentioned above, i would advise working on the rear delt as it is often negelected for the bench. i've been training shoulders twice a week recently, with focus on the rear delt, doing reverse pec deck and upright row. we also do narrow grip bench which will strengthen the triceps and are sometimes the weaker link of the bench press equation. we also bench only once a week.
i think you're lifting maybe a bit too high reps towards the heavier lifts, we start with set 1 @ 10-12 reps, set 2 at 8reps set 3 at 6 reps, set 4 at 3-5reps, set 5 at 3reps...set 6 at 1 rep then 2 sets of pause techique or narrow grip. once every 6 weeks or so we go crazy and lift say 75% of the max weight for 15-20 reps or until burn out...
also try block work, so you're only lowering the bar to about 2 inches above your chest..i havent yet used this technique - saving it for new year.
do you wear wrist wraps? i found this really helped keep my line/balance.
last monday i benched 225 for 5 reps and i already beat my own target lifting 105kg for one about 2 weeks ago, so the tips above worked for me!