It figures that after we both finished The Enterprise, you'd stumble upon my other most loathed mission :^) I finished this one though, so I'll try to help..
Switcher's House:
spoiler:There's a little shed somewhere near the clock tower I think... It has a bunch of boards laying around in it.. If you look in there, there are rope arrows on the floor..I think under the boards in the back... It's dark, so they're basically impossible to see, but they're there... Grab the rope arrows.. You probably have the right window.. It's basically a window, and to the side of the window there's a little wooden beam sticking out so you can rope arrow up and then jump in through the window.. That will take you to Switcher's house...
Warehouse:
spoiler:I believe this one is way in the southwest corner of the map, so use your compass and head southwest... It's tough to get inside.. Basically, there's a house with glass windows and the warehouse is across from it.. I think there's a broken carriage or something in the alley by the warehouse... You have to get into the house through one of the glass windows (you'll know it's the right house because there is artwork on the wall that you can click on for a caption), go up through the house and you'll find a way out onto the roof.. Then, you have to go and jump on the little ledge sticking out from the warehouse, follow it over, and lean in the open window to try and get the key (you can't get inside the window..you just have to try to lean in far enough to snag it)... Then you can go inside and use a little ingenuity to find the hidden weapons..
As far as the button goes, I have no idea.. I think I found the key but couldn't find the button, either.... I managed to beat it no problem though without finding the button...