fuddinator

How old is it? If it is still under warranty, try to get a replacement. If not, odds are be prepared to get a new mouse. 

My first question is are you renting or do you own? 
 
Also, how handy are you when it comes to home repairs and DIY projects?
 
If you rent and/or not handy, you can try a powerline adapter. Use the powerline adapter to hardwire the new router and then use it as an access point.
 
If you own and are handy, you can always hardwire your house. Granted my house is a small single story at 1200 sqft, I made 16 runs throughout my house to a patch panel in the utility closet during a 3 day weekend.

Your best, quickest, and easiest solution is to go powerline ethernet adapter. It basically uses the wires in your house as ethernet cables. This allows you to hardline your new router to your old one in AP mode.
 
The best best thing to do would be hard wire the house but considering the size of your house, thats not a quick weekend project. If the money was available, I would just hire someone to do it. Yeah it costs alot but hassle free. I am an airplane mechanic by trade and a lot of times I take my car to a mechanic because sometimes, I just can't be bothered. Spend all day changing an oil pan gasket, or drop the car off in the morning, spend all day playing in my shop on fun things or playing my pc and pick up the next day.

For lefties, your are pretty much stuck with mostly ambi mice with symmetrical designs. I know for ergonomic mice, razer has a left handed version of their deathadder and naga.

First I would wait. You already have a good GPU and dont need to upgrade before the next big release summer this year.
 
I tried SLI before and to me it isnt worth the hassle. First you are at the mercy of nvidia for proper game profiles. Scaling per game is hit and miss. I find it much easier and simpler to stick with one high end gpu than 2 mid range.
 
Now if you are trying to push 4k at 60hz or 3 1440p screens at high framerates then SLI makes sense. Me for example, I play 1080p at 120hz and my 780ti is still perfectly capable. Im waiting for pascal to upgrade.

Go with the desktop. It looks decent but needs a dedicated gpu from what i can tell. A 750ti or 950 would be great cards for those games depending if your psu can support the extra power of the 950

I would avoid wireless. Batteries always die at the worst times.
 
Logitech makes decent mice all around but i much prefer Mionix. They have good sensors and I prefer their ergos. The Mionix Naos fits my hand like a glove.

I had a deathadder 3.5 and 2013(not sure?) and they were decent mice. My only problem is after about a year or so with each the left click wore out and would double click randomly. Lost a lot of gear in DayZ. You can fix it but it was tedious. I also found it rather slick for my clamy hands and it caused my hands strain after time. Everyones hand is different.

I had a deathadder 3.5 and 2013(not sure?) and they were decent mice. My only problem is after about a year or so with each the left click wore out and would double click randomly. Lost a lot of gear in DayZ. You can fix it but it was tedious. I also found it rather slick for my clamy hands and it caused my hands strain after time. Everyones hand is different.