speeding up my runtime on a c6713.

I'm running way too slow, but I know I've done a few things
inefficiently on in my C program.

1) I ran out of IRAM memory so I moved all my variables to ERAM.
What did this cost me?
1A) How can I pick and choose where in memory my C++ variables
reside?

2) instead of using 'float variablea;" I used 'double variablea;'
what did this cost me and what can I expect by changing all my
variables to float (32 bit vs 64 bit.) ?

3) How else can I effect the runtime of my program, I see there is a
clock properties, setting, I know by removing all my fprintf's I pick
up save some 20% of the runtime, What about switching from debug to
release mode, or something else I haven't considered?

.