Ouch, sounds like this phone has been a real pain for you dysfunkshun but I do have some suggestions for you.
For the Wi-Fi speeds, you can try going into your Settings and open up your list of Apps to find the Google Connectivity Services and clear the data and cache from that app. This application helps with network connection and this could resolve the speed issue by doing this.
For the MMS, I would suggest using just the pre-installed messaging application and removed the 3rd party apps. You'll also want to make sure you have all the correct APN settings that can be found on this link.
After checking those settings, I would make sure you have a strong 3G or 4G connection with 2-3 bars of signal then retest the MMS. It wouldn't hurt to try it with another person as well as another image to make sure the picture itself isn't the source of the issue. A master reset would be the last thing you could try on the phone to resolve the Wi-Fi and MMS issues.
As for the fingerprint scanner, we've been informed that LG is developing a software fix to help with that. It tends to work better without a cover on the phone, so I would encourage that you remove it if you have one. You'll want to keep an eye on the V10's software page for the update.