Hello Skyn0s,
This is what I did to stop my Harpoon wireless mouse from constant double clicking (your #2 issue):
1. I made a post here on the forum asking for help, like you did.
2. One of the Corsair forum support people sent me a private message and asked me to write up a 'Support Ticket' (which is at the top menu of this forum).
3. I created the support ticket. That was a week ago. Maybe the Corsair support team is over burdened; they have not gotten back to me.
4. While waiting for help via the Ticket system, I searched the forum for 'Harpoon double', and found a temporary fix that worked for me. I used old (legacy) firmware for the mouse and the dongle, and forced the update within the iCUE application. No more double click, and the mouse is usable for my needs. I think the mouse is fine, but the software and/or firmware is at fault.
I expect that Corsair will fix the Harpoon firmware and iCUE app - eventually - and I can wait. My mouse is 6 months old, and I really like it. However, if I had just purchased it 2 days ago (like you) I would return it and ask for a refund and then buy some other brand of mouse that does not have unsolved issues, and that would eliminate the need to wait for a fix in iCUE and the firmware.