Write your own powershell and schedule it with the Task Scheduler:

http://www.sqlmusings.com/2011/03/28/how-to-download-all-your-ssrs-report-definitions-rdl-files-using-powershell/

I use this:

http://weblogs.asp.net/akjoshi/archive/2009/01/29/using-rs-scripter-to-create-deployment-script-for-reporting-services.aspx

Hopefully it help you.

This may be an Excel issue itself, my recommendation is to test the excel output in different Excel(s), 2007,2010,2013.

You can't change font for the tool-tip, and the limitation is 512. What you can try is JavaScript, here are some references for you:

http://experiencingmsbi.blogspot.ca/2011/08/using-javascript-in-ssrs.html

http://blogs.infosupport.com/reporting-services-javascript-injection/