155° is a bit high for the mash temp, but not out of line if you are brewing a sweet stout. I would shoot for no higher than about 153° for a sweet and 151° for a dry. You racked after only one week. I think you just racked too early. When I first started all grain several years ago, I religiously stuck to the schedule of one week in primary and two weeks in secondary. I now seldom rack out of primary in less than two weeks and sometimes leave it in there for 3 or 4 weeks and skip secondary altogether. Since letting my primaries go longer, I have gotten better attenuation and more consistent quality. Don't worry about leaving your beer in primary too long, unless you are considering letting it sit on the yeast for a couple of months. Your beer should be just fine. Just let it sit for another 3 or 4 weeks, the gravity should come down on its own. When you racked you still had plenty of yeast in suspension, but since you racked off the yeast cake early, it will just take an extra week or so for fermentation to finish out.
Just a note on fermentation, it is good to let the beer sit for another week or so after you have reached your final gravity. Even though the yeast is done producing alcohol, it is still actively metabolizing many of the fermentation by products. Many refer to this as the yeast "cleaning up after itself". If the yeast is not allowed to finish this process, you may get some "off" flavors from those by products.
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