1. Saved the report document into a session variable and load it back in after postback but;
2. Disabled the parameter prompt on postbacks.
3. To fix the paging issue, I had to move the code from the Page_Load to the Page_Init (found the solution here: http://www.crystalreportsbook.com/forum/forum_posts.asp?TID=2709)

        protected void Page_Init(object sender, EventArgs e)
        {
            // Exit if the session variable containing the report document is null (or does not exist).
            if (null == Session["ReportDocument"]) return;

            // Set the Crystal Report Viewer source to our previously saved report document.
            var crdoc = (ReportDocument)Session["ReportDocument"];
            crViewer.ReportSource = crdoc;
        }

        protected void Page_Load(object sender, EventArgs e)
        {
            // We only want to see the parameter form on the initial page load.
            crViewer.EnableParameterPrompt = !IsPostBack;

            // We only want to continue on postback and if the session variable containing
            // the report document is not null (exists).
            if (IsPostBack && null != Session["ReportDocument"]) return;

            // Load the rpt file from the sharepoint library and display it in the viewer.
            // The report document is saved into the session variable in this method.
            DisplayReport();
        }