i am not sure what you are trying to do here. you are already getting what you paid. we all have things we want but can't afford to pay for. i mean i would love to replace my i10 with the new i20 but i can't afford to make the switch. should i get this upgrade just like that because i want it? or i need it? when i cannot pay for it? things do not work like that.
just because broadband services are a virtual product, doesn't mean that hacking your connection to get higher speeds is not theft. i am sure you can find a more suitable community elsewhere on the internet for your queries. this is not the place for this.
also i find it hard to believe that your family members can saturate your connection so much that they leave only 2mbps for you. schedule your downloads for night time when everyone else is asleep. 80GB on a 100mbps connection would take less than 2 hours at peak speeds. even if you get half the speed, you are still looking at a time period of less than 4 hours per download. i am sure you spend more than 4 hours on these downloaded games and you are not downloading 100 80GB games on a monthly basis.