after pasting my gameboard tielsto the foam core the board warped a bit (too much glue?  i didnt THINK i used too much).  any suggestions  on how to reverse that without breaking it?

Its probably not that you used too much glue but rather the kind of glue you used. Some white glues like "Elmers" have a really high water content and tend to warp everything they touch. Find yourself an adult version of white craft glue, like the kind used for wood. I’ve found that "LewisCraft" white craft glue has a low water content and does the job well.

There is only one fix that I know of and that is time and weight. Grab some heavy books and place them on the back of the foam core overnight. This should fix your problem

i discovered through trial and error that breaking the board's core in places (ie by walking on the board) i was able to straighten it out.

on my other board i think ill probably just use a good-sized dot of glue at the corners of the pages.... should hold just as well.

For the tiles you can use spray adhesive as well.  Avoid any of the "repositional" spray adhesives and stick with heavy duty stuff.  The brand I use is Scotch #77, which makes a permaneant, non-warping bond.  I've also used it to mount some Cheapass Games game boards to foam core and they've held up great for years with no warping whatsoever.