FiOS upload problem: my personal battle with Verizon

I am experiencing problem with my FiOS, cannot upload files >2-3 MB. For instance, I cannot upload any videos on Facebook and have huge delay of uploading any videos on YouTube. I cannot send attached file via e-mail if file is bigger than 3 Mb...

I have ticket opened with Verizon, but they cannot figure out what's wrong. I have this problem about 2 (!) years. Is that a time to switch to Comcast?

I will be updating the status of the issue here.

So far they suggested replacing router. I did. 2nd time for the last 2 years. The problem is still there....