How long before you want to start the CRNA program? If it is soon then you should go ahead and switch to ICU.
Recognize that while the CRNA program in that school will accept the courses taken through the ACNP program, other schools
probably won't. Just FYI if you decide to go through a different school.
Your GRE is low for most CRNA programs, I believe that most want as least a 500 on both verbal and quantitative, the analytical section is not as important but getting it up can increase your overall score. I would buy one of the Kaplan/Petersons books, study it, and re-take the GRE, this will put you in a much more competetive position.
Ask the program director what the view on part time ICU nurses is. Make sure that it will not be something they look less favorably on in the selection process.
GPA looks good, you should have no problem there. Your age is not an issue, the ages in my class range from 25y/o to 50y/o.
Hope that helps a little, good luck!