With regard to metabolism and re-gaining of weight, SailorDoom pretty much said what I was going to say.
About the plateau. When losing weight I tend to zigzag my calories. When I reach a particular annoying plateau I go back to a maintenance level for 3 to 5 days. That always helps me. YMMV.
The only way of finding the limits of the possible is by going beyond them into the impossible. -- Arthur C. Clarke