You fail to see the whole picture yet.
We DO NOT KNOW what your network setup is, or looks like. We can’t guess and don’t like to guess!!! 
Since this is a speed related question we need to know ALL the info possible about your network setup.
Yet so far you didn’t answer some basic questions:
What kind of connection to Internet do you have? xDSL, cable, fiber optic etc?
What is your Internet connection’s advertised speed?
Opposed to that, what’s your connection’s tested, real speed?
What kind of equipment connects you to the Internet? Is it a router and a modem? Is it a just a modem? Is it a modem+router integrated device? Is it something else?
What make and model is it?
It is well specified in that announcement that the lack of the said information will result in your post being ignored, so the fact that we’ve answered it so many times just to ask for more info, is proof of our courtesy.
Along with not having all the above info, now you come and say:
Take it from the fact that I have used the setup for both connections…
and
Also speed test is not accurate for the higher connection for the traffic that goes through but the 1.5/768 Mb down/up is accurate and seems to be affected in the same fashion and this connection is dsl through a router, the other I can’t be sure of.
When did you EVER tell us that you’re using 2 different Internet connections? This is even more confusing now.
Do you have 2 network cards in your computer?
Do you use both connections simultaneously? What type of connections are they?
… without craping out the rest of my network.
So, do you have a LAN too, now? How many computers? Are others of them using file-sharing clients too?
If you’re part of a LAN, how is it connected to the Internet?
Is any of **your **Internet connections separate from your LAN connection? Are you the administrator of your LAN or is it wider (the whole building)?
Do you see now, that we know NOTHING about your network setup?
These are the questions to which you should have provided an answer from the very beginning.
It’s very frustrating having to post over and over just to ask for more info. And the mods of this forum have to go through dozens of posts on a daily basis, not just yours.
So, if you don’t help yourself and increase your chances by giving as much info as possible you’ll get nowhere.
Because nobody is happy about having to write posts longer than yours, just to ask for more info or clarifications.