I think R1 tires are a good pick for your needs.
I'm assuming this is an HST tractor? I think all the 4R tractors are, but I'm not certain. I think an HST is very important for your use.
After owning 3 different tractor backhoe attachments over the years, I'd would suggest you not waste your money or time on one. I just kept hoping they'd get better on bigger tractors, but they are not. They are just too much of a compromise. If buying a used mini ex isn't viable, then I'd prep and accumulate projects, then rent one for a week or whatever. Tracking a mini ex down a bunch of woods roads is not a big deal. I regularly move mine 1-2 miles. A 2 mile trek will take 30-45 min. Just plan your work so you aren't moving around more than necessary.
I'd ask to see the Deere records for the machine. It should show the in-service date which is when the warranty starts, plus the end of warranty date. I'd be surprised if there is any warranty left if it started when it became a demo roughly 4 years ago. My 6 series Deere has a 2 year warranty.
Confirm the machine is really a Demo always owned by the dealer, and that it wasn't actually sold then traded back.
The records should also show who all work that has been done on the machine. Make sure all the prep was done as expected, plus follow on service. It doesn't have a lot of hours, but many service tasks are time based as well as hours based.
And especially check the records for any repairs. I would also recommend personally checking the torque on all the loader frame and tractor frame to engine bolts. There are many reports of these bolts coming loose, falling out and all sorts of consequential damage. I would witness mark all of them after checking, then keep an eye on them.
I think you will discover pretty quickly that a hydraulic top link for the 3PH would be super useful, not just for hooking up implements, but also for adjusting their level as you work. I find it's one of the most commonly used controls when working with a 3PH implement.
Just a quick comment that the "deere hitch" on this tractor is NOT the same as a "Euro" or "Euro/Global" hitch. There are some similarities, but the Euro/Global hitch doesn't enter the Deere line until the 5 series, and becomes common place in the 6 series.
Make sure it's clear whether transportation and/or road service is part of the warranty/extended warranty. If not included, and if you can't trailer it yourself, this can create a bunch of out-of-pocket expense for "free" warranty work, especially if the tractor has to go back to the dealer multiple times to find something, which seems to be all too common.
Check up on the dealer's reputation for service. Dealer hate seems to be a growing thing, especially as family dealerships get rolled up into corporate behemouths.