The best way to cut acrylic is on a table saw using a 7 1/4" paneling blade. Make sure the teeth on the blade are in line with each other and not offset. Offset teeth will cause the acrylic to chip. Run the blade so that it comes through the acrylic about 1/8".
The best glue I have found for acrylic is Weld On #3 and #16. The #3 is very thin and your parts will have to fit perfectly to use it. The #16 is thicker and will fill gaps...needless to say, I use mostly the #16
HD is too high on their acrylic...check your local glass shops. You should be able to buy a sheet of 1/4" for about $80. You might buy scraps of the right size for nearly nothing depending on how large a sump you wish to construct.
The best tool for making the U tubes on the overflow is your credit card. Seriously, I have tried to bend that stuff and have not had lots of luck with it. You can bend sheet acrylic with a heat gun, but you have to be really careful not to overheat it or it will bubble up. I just buy the U tubes though. You can bend PVC
easily with heat, but I like the clear tubes better.