Re:Single arm deads for old man
Using a DB wont put significantly less pressure on your lower backs since you ll have to keep yourself upright.
At 38 there is absolutely no reason why you shouldnt be able to deadlift. Id look at your form and try to work in cycles. Some work on flexibility/mobility might help you to keep a better starting position. Also strengthening your hamstrings will stop your hips from shooting up, which places extra pressure on your back.
In a month you could work up to 110, 120, 130, 140kg for reps. Next month 112.5, 122.5, 132.5, 142.5 etc etc.
Equally you could try deadlifting once every 10 days/2weeks.