(1) Your business isnt provided a customized system so it isn't a professional service.
(2) A web portal or a web 2.o application is more a service than software, but state tax laws have dealt with it similarly to software.
(3) You could argue that your service is really a report generating service because your helping clients generate management reports on the status of their projects. Reporting services are almost always taxable sales.
Hope this helps, i'll probably post that matrix whenever i find it haha.
I'm a professional that uses these legal research tools and I cant even rely on them. I have to basically do all the work because their conclusions are not reliable when ur client is audited.
Tax, law and etc are just weird areas where you cant automate it on a level higher than turbotax. I think it'll always require a person on the other end to do it just cause its such a labor intensive field that is never the same result on a consistent basis.