I accidentally chose an incorrect person in the In Memory Section. Is there anyway I can correct that so he doesn't show he is deceased when he is really still living?

Yes, Choose Edit Site Pages, then Edit In Memory.

You'll see the list of classmates that are marked as deceased.

Find the one that is incorrectly listed and click on the 'DELETE' link. That will delete them from the In Memory page. It will not delete their profile.

Dave

Is there any way to put all deceased info on one page and is there a way to take off the option to post comments?

Yes, there's no reason you have to use the built in In Memory functionality. Just click on Edit Site pages and remove the checkmark next to your In Memory page. Then using one of your Customizable Links rename the page name "In Memory" and put all the information you want on the page.