>how are you 100% sure that you aren't being watched by your ISP at least? :)

I'm in a similar position so I'll have a shot at this.

Local ISPs tend not to log detail (no business case) and they are legally prohibited from monitoring communication anyway. So the only viable scenario is give the ISP an IP and ask for account owner (IP vs Account is logged). Which they won't do without a warrant (image risk). That combined with the messed up court system means that nothing makes it through the red tape & hassle unless its something intense (child trafficking etc)