I'm 40+ and have a TM of almost exactly what yours is on DL. I also struggled with the volume, because I had never done DL's for many reps before and always worked up in sets of 3's or even singles.
Here's what I have done: gradually add the volume to the supplemental DL's. I am running Krypteia and started with 5x3 and held this for the first cycle as the supplemental volume, then did 5x3, 5x4, then 5x5 on the 2nd cycle of Phase 1 (which used FSL). On Phase 2, I did the first cycle at 5x5, then have been increasing to 5x6, 5x8, then 5x10 (this phase uses BBB sets as supplements). It has worked great, and I've adjusted to the volume when at first I wasn't sure I would be able to. Today, it's DL day (333 of cycle 2, phase 2), and I'm doing the 5x8 as the supplement at 225 lbs.
Another thing: work on controlled lowering of the weights, and touch-and-go reps. Don't let the weight crash down. I think this keeps your core engaged and gives you more work on the lowering portion of the lift.