1RM-Deadlift

I think what powerllifter has for you is fine. My only changes would be to start with a lower rep scheme and include a deload week prior to the meet. I have found that deadlifts over 400lbs. take a toll on everyone, regardless of your level. So…

wk 1: 6,6 @ 6RM
wk 2: 5,5 @ 5RM
wk 3: 5,5 @ 5RM
wk 4: 5,5 @ 5RM
wk 5: 3,3 @ 3RM
wk 6: 3,3 @ 3RM
wk 7: 3,3 @ 3RM
wk 8: 2 @ 2RM
wk 9: 5 x 1 @ 60% of opener, working on form
wk 10: comp

Week 9 lets you do five singles working on your approach, getting set, and executing a clean pull. Working at 60% lets you do this without stressing the CNS, so it acts as a deload. Everyone deloads for meets…there’s a reason for it and I think you should take it easy the week before and focus on form.

Also, You don’t have to wait until competition to make gains in your lifts. If your xRM goes up from week to week, go with the new weight. I.e, if week 5 you squeek by 3,3 at 475, but week 6 you pull your 3,3 with no problem, try 480 x 3 your first set on week 7. If it feels good, do it again. If not, drop back to 475 for the second set of 3.
As for accessory exercises, I would add to Powerlifter’s rack lock out sets, one or two singles (in weeks 4-7 only) from about six inches above the knee with a weight that is 110% - 120% of your opener. These work the last few inches of the lift, working your grip, your finish, and let get you comfortable with a heavy load. Your 1RM won’t feel so ridiculously heavy in competition. You will develop the confidence that if you can just get the bar a few inches above your knees, you can finish the lift.

Finally, I would say that 500lbs. is not a novice lift for a drug-free 18 y.o., it is a respectable lift. You may not win the meet if there are experienced powerlifters there, but you will see many teens that do not go over 500lbs. in that weight class.