Mailchimp configuration

I need to correct an existing signup form that I have been using. Right now it doesn't matter what people select, they are only able to choose one of the three options even through they should be able to check all that apply. It used to work but doesn't now. I need to fix this as soon as possible. Second issue is that we use mailchimp to do several things. 1. tell us what kind of emails people want, They have three choices. 2. Over the course of a year, we will send between 6 and 10 messages to about 1,500 people. I want to be able to upload to mailchimp a list that updates the mailchimp list with a tag that says these x number of people participated in one of our activities. That would update the tags for those that are already in the list and will add people to the list that are not there already. 3. The only information that I maintain is email, first name, last name, and which activities they participated in. I need help organizing the account so it does that and that I can easily send a campaign to just those that want updates only or just those that want one type of email, or just those that participated in activity x. Also, we don't have first name or last name for every email. I would like to be able to send an email to those who we are missing first names and ask they to tell us. Those are the things I need to fix and organize. If you are interested in this project, please let me know.