second front derailleur doesn't fit, what am i looking for?

I recently upgraded my 2010 gt aggressor to sram x4 shifters only because i had an 8 speed cassette and the shifters seemed a fair price, now i'm looking to change the front mech as its seized and is far too old to consider taking apart and fixing. It's a shimano altus 3speed but i understand that's not ideal now i'll be using the sram shifters. Firstly I brought a bottom swing deraileur because i misunderstood the term dual pull and at the same time got the two different types of pull confused. The derailleur fit too high and whilst trying to fit i realised that the cable run on my bike also runs down the left hand side(looking from the back of the bike ) so the opposite side to the mech and cranks. I thought i now realised that I needed a top swing top pull deraileur and assumed they all pulled from the left. Just purchased my second derailleur - a sram x9, now i've opened the box and seen that the cable run is still on the wrong side i dont even know what to look for.

I'm bad at explaining myself so I'll quickly sum up because im not even sure if i understand myself...

I need an 3sp front derailleur thats compatible with sram x4 shifters, left side cable pull on the frame, top swing, top pull derailleur. Or even is it possible to mount the deraileur witht eh cable running diagonally across the seat tube and function this second derailleur that I've brought?Any advice at all would be appreciated because mates have come out with the usual third time lucky advice and I'd just like abit or reassurance before place this last order from chain reaction\wiggle\ebay\amazon. Also it would be nice to finally change out of my seized gear two on the front considering i live in abit of a valley... Thanks in advance!