Dave in answer to your questions.
1- GoodReader app (iirc) is free and you can use that to read PDF and store them. Also iBooks app stores PDF I have about 90 on my iPad. Once iOS 4.2 is released you will be able to do wireless printing.
2 - Dont quote me but I'm pretty sure iOS 4.2 has Microsoft exchange support so I would assume you could use business server.
3- Not sure but if you have test website pm me the details and I can try for you.
4- PDF reader Pro will definately open tiff files. I think good reader does too but don't quote me.
5- logmein ignition app allows you to remotely access a desktop using the iPad. Needs wireless or strong 3G signal though.
Hope that helps. Sorry can't be more exact but I don't use my iPad in the way you are planning and only know what I've written from experience and previous research.
Carl