Macpro 2009 wont boot into anything except Windows

first thing to try is a PRAM reset.

Hold these four keys startup:

Command-Option-P-R

keep holding those four keys for a long time, until you have heard four sets of chimes (or it stops chiming again.)

the number of successful chimes you can coax out of it is key, so report whether you got four, or fewer that four, and how many.

the simplest thing your Mac can do is to boot to the startup assistant, often referred to as the "Boot Picker".

hold Option at startup using wired keyboard directly on the chassis. it should draw a gray screen, then look around inside and discover any bootable Volumes, and add an Icon for each one it finds. After several minutes, the watch cursor turns into a regular pointer.

if it draws icons, what are they?

Mac Pro 1,1 and 2,1 can run up to MacOS 10.7.5, without hobbyist hacks to get access to firmware add-ons.