90% of his errors are throwing, so 1B seems obvious, if he can't fix the arm issues. Throwing issues at 1B are not as much of an issue.
He's got a plus glove and range. That's not just my opinion. The data backs it up. Believe what you want, but he's no where near as bad as you think he is.
If he was a 24 year old in AA, you'd say give him more time, but you are penalizing him for being called up at such a young age. He showed growth from year 1 to year 2 and from year 2 to year 3. He regressed in 2020, but that was one Eff'd up short season. A few mishaps in ST'ing is not reason enough to bump him to DH, where we are paying someone $22M to play, and JD can't play anywhere else but DH.
There is no other option but to jerk him to 1B with less than 3 weeks to opening day. I'd argue that is no option, either.
Live with it. If he sucks on D this year, the move to 1B- not DH- will be obvious and successful. Book it.