My friend's son benched 505 last week. He is a serious lifter, a hunk of granite. Going for your one-rep max in powerlifts (bench, squat, deadlifts) is not a great idea for us "functional fitness" people. There is no need at all to do it except as a feat. For general fitness, keeping powerlift reps in the 3-10 range is correct for heavier weights.
You can guess your one-rep max by extrapolating from your 3 or 4-rep max. I do not have a lifter build (have a runner's build), but I go for barbell deadlift one-reps about twice a year, just for kicks and to be stupid. I discovered that I can not deadlift 275 lbs this week - just up to my knees. Damn. I know a gal who deads 300 lbs. Strong, fit gal with no visible muscle mass. Perhaps I did not warm up for it right...
With the powerlifts, always warm up light and work up, usually 5 total sets with a good rest between sets. If you want to be stupid like me once in a while, How to Warm Up for a One-Rep Max
If you like to use a trap bar for deadlifts (I do, occasionally), you can move much more weight than with the barbell. I have never tried a one-rep max with the trap bar.
Below the fold, a few words on other, non-powerlift pure strength exercises -
There are many non-powerlifts to fit into the pure strength component of a fitness routine, but the 3 powerlifts are the core. For my age, each powerlift (and each strength exercise below) only really wants once/wk. After all, you are doing 2 hrs of calisthenics and maybe 2 hrs of cardio during the week too.
What are some other pure strength exercises that are worth doing 3 or 4 sets of each week for strength maintenance or improvement if you have time?
Pull-ups and hangs, or pull-downs if you can't do pull ups
Push ups (can be viewed as a calisthenic or a strength exercise)
Dumbell Rows (and cable rows)
Curls (just for vanity)
There are plenty more, but there is only so much time if you commit 2 or so hrs to pure strength/wk. Mix them up, but always the powerlifts.