Hi there jim, I can't answer all your questions with certainty but I can certainly try to answer a few:

1. I should think it wouldn't take Comodo too long to assess a submitted file. To be on the safe side I'll say a week or less, but thats just a guess. Only the people who actually do it would be able to say for sure. Maybe one of them will chime in.
2. Comodo does not advise users directly about the outcome of the submitted files. You can just assume its not safe, but where's the risky living in that?

Once again, I at least do not know the certain amount of time necessary to analyze a file and deem it safe or unsafe therefore I can't venture a guess as to what you should do there. I suppose its what you're comfortable with. By and large, many of the files are probably safe.
3. Due to the uncertain nature (at least for me) of adding the files to the safe list I would hesitate (read as: I can not) actually advise you to delete the files off of your hard drive just because they have not been added, especially since one really does not know the amount of time necessary to do this.
Hope this has helped you somewhat, perhaps someone who knows more than I do will drop on in later on.
Dave