Since you are only doing it for 2-3 weeks, you will be alright. If you're strength drops a whole lot it is most likely due to glycogen depletion and loss of some leverages. If you just doing heavy lifting w/ long rests it may take that long to get depleted in the first place. You shouldn't have to worry about muscle loss if you are still training heavy.
Don't let the low calories psych you out.
You could reset a bit, and w/ typical volume work back up to your current 3x5 and 1x5 RM's at the end of the diet period. Thats probably what I would do, just to keep some semblance of forward momentum.