Goofinder...
I think after tasting the beers at/in the swap, I'm going to need to qualify my not liking bitterness a bit better. :lol: There were quite a few beers that were more bitter than my usual preferences that I quite enjoyed. (I tried to remain open minded, but there were some which even surprised myself).
Looking at the recipe, I think you hit the nail on the head about it dropping to a lower fg than you were going for as being one of the main reasons I found it bitter. Your late hop additions are not too dissimilar to mine; same times, same weight/volume on the f/o, slightly higher weight/vol on the 20, but not by a lot. Slightly higher BUGU than what I bitter to, but again, not by enough to push the perception OTT for me. (0.71 compared to my usual 0.6-0.65). When changing over to BV, though, is where the difference becomes more noticeable. From your 1046/1010, it came in at 1.6BV, which would be comparable to 0.8BUGU, which would have altered the balance a fair bit from what BUGU would normally indicate. (the extra couple of points would have given ~1.4BV).
All that is making some assumption as well, though, particularly in relation to actual boil gravity, utilisation, losses, etc. If using Tinseth for the calculations, reasonably accurate knowledge of the losses plays a role because of the way he has done the formulations, and the inclusion of what he calls 'bigness factor' (basicaly, tinseth formulation uses the loss to evaporation and the length of the boil in association with the projected initial boil gravity to work out an average utilisation for the boil due to the changing gravity). So the 'actual' IBU in the beer will vary quite considerabley from any formulation of that, anyway. So numbers can only go so far.
And at the end of the day, when it comes to your own beer, your opinion is the important one. I'm a firm believer in brewing to taste, not to style. If it's right for you, then it is right.