I didn't bother to read all the responses as I am short on time, and it looks to me to be mainly about people defending their positions.
For what it's worth, I understand that to many people, it's simply insane to take day trips involving a large number of hours on trains, in many cases with much more time spent on trains than at the destination itself. I will just say that to me, it isn't insane at all. My limit is roughly 3 to 3.5 hours of train time each way (for a total of 7 hours), but I like to get back to my hotel fairly early in the evening and go to sleep by 9 or so. If I were younger and didn't mind staying up until midnight, I might be happy to expand the train riding to 4 hours each direction. If I had a hotel in Tokyo and a JR Tohoku Pass, I would have no problem getting several times the face value out of the pass, and I am sure I would have a marvelous time.
So I honestly don't see any need for the OP to return his rail pass or pay for double accommodations. It's a matter of picking suitable day trips, is all. Obviously, you have to plan things out very carefully including any local transportation at your desination, opening and closing times of venues, time of the sunset, etc. But why should he return the pass? It sounds like something I might buy myself for a week of travel based in Tokyo, and not as a mistake. I would just plan everything out before buying the thing (I might go for a different pass instead--but I might not).
I am actually looking at day trips from Tokyo on my next trip. One of them will probably be to Kyoto with a brief stop in Nagoya (put that in your pipe and smoke it), but that isn't an option with the JR Tohoku pass. Another one I'm looking at is a day trip to Aquamarine Fukushima, possibly visiting some other sites in that immediate area. (That would actually be a very easy one.) Also, I recommend Yamadera as a day trip from Tokyo, and this could be combined with a visit to Ichinobo at Sakunami Onsen and/or possibly a visit to the Nikka distillery. The timing of all that has to be carefully planned (Ichinobo has a limited window for day use, and it looks like they are closed once a week or something). I once did a loop from Tokyo to Yamagata and then Sendai and back, and it was fairly enjoyable. Sendai has some excellent restaurants. (I have gone up there from Tokyo just to have lunch at my favorite. In fact, I've done that a couple of times.) Matsushima is a nice day trip from Tokyo, although I can't say it is my favorite. I've done Morioka as a day trip but that was for a festival. (Otherwise I can't say Morioka is the most exciting destination. Nice town, but... )
I also think Kakunodate would be a good day trip from Tokyo. (I have only done it as a day trip from Sendai but I would seriously consider doing it from Tokyo. ) Personally I would not combine it with Akita; that does sort of seem like too much. Aomori I would do but probably stay in one place and pick some interesting sights for about 4-5 hours of sightseeing (there is a historical museum/site I was looking at once but I've forgotten the details and don't have time to look them up).
It sounds like the OP is trying to balance some closer day trips with longer-distance ones, and that sounds like a good idea to me. On my last trip, I had about a week where I took rather long day trips every day for about a week and I have to admit that I got kind of tired (but not tired of riding trains). I wouldn't have changed a thing, though. It was just fabulous. I love having a home base to return to every night.
Another suggestion is to look into some of the neat limited express trains and simply enjoy them for the recreational train riding experience. Look at JR's page on "Joyful" trains and see if any of them might be options (I don't have time to see if they are within the zone covered by the Tohoku pass). It is not an exhaustive list of LEX trains, though.
https://www.jreast.co.jp/e/joyful/index.html?src=gnaviSo the bottom line is that everyone is different, and there are some people for whom long day trips are not a bad idea. I don't think it's necessary to jump all over someone who is considering that, and I don't blame the guy for getting a little defensive. If he was proposing an itinerary where he changed hotels every night, people would jump all over him for that...