I'm not familiar with Addison's disease or its impact on training, so can't advise you in that regard. Assuming it's minimally impactful, I'd add a few pounds and implement the technique changes above. A few more pounds as opposed to the weight you're currently lifting is unlikely to increase your chance for injury significantly. And for a guy your age and size, this is really not a whole lot of weight to deadlift anyway.
I would recommend not removing weight from the bar. In my (random internet stranger) opinion, you need some weight on the bar so that technique becomes an important lever in actually completing the lift. Too light and you may end up manhandling it without actually having to learn to control technique under a load. You need something to trigger your mind into going, "wow, that felt much easier!"
The most important thing for maximizing efficiency and minimizing your chance of injury is to get your back straight and tight. Definitely get a belt and learn to use it correctly. For the deadlift, the best belt advice I got was to start at as tight as you can get the belt and then back off one notch. This gives you enough wiggle room to breathe at the bottom while still having something to brace against.
The ones that are wider on the back are shit. Get a 3" Dominion Strength Double Ply belt. You won't believe the difference (give the Dominion Belt a little time to break in).
One last thing on the deadlift technique. We call it a "Pull" because of the movement pattern it emulates and trains, but don't get the idea that you need to pull on the bar. "Pulling" on the bar sets you up to push the floor away. Don't cue yourself to "pull". Cue yourself to pull all the slack out of your arms, back and the barbell itself, and then push the floor away. Do this by telling yourself to use the barbell as leverage and drive your heels through the floor. Read here: The Deadlift: Pushing the Floor | Mark Rippetoe