You don't have to kill yourself. It's far easier to just build another nether portal in the nether where you want it to be (assuming the coordinates match up with your base or within 128 blocks (ignoring height), which is just 16 blocks in the nether), then destroy the first one. However, if your base's coordinates match up with a large lava lake in the nether with no good solid ground nearby you're likely out of luck and would have to move your base or try to make a bridge in the nether. 500 blocks in the overworld is only about 60 blocks in the nether.
Right-o, I was going on the assumption that the OP couldn't really travel at all in the Nether. Been a while since I made portal transport, but the wiki
http://minecraft.gamepedia.com/Nether_Portal points to 1024 overworld blocks to generate a new portal on the Nether side.
Did you try that with fuel? Oil is not anywhere near as good as fuel. Fuel would have given you 6,000,000 RF. Also, how long did it take for you to get the full mana pool? How much steam exactly did you have? A max sized boiler will produce far more RF/t than a few endoflames... and can run on fuel. The mana fluxfield does not obsolete every other power source, it's just very convenient considering you get a lot of mana producing flowers for free and are encouraged far more to progress in Botania than in buildcraft or railcraft. Any setup that produces a considerable amount of RF/t via the fluxfield will either take up a lot of space or be less efficient than alternatives.
I considered it.. but was thinking in terms of simplicity and infrastructure. With endoflames alone, I can feed a 7x7 farm with a single dropping system, hooked up to a coal farm / auto-crafting coal blocks. I'm not saying this is at all efficient, but since I can easy scale up the coal farm to accommodate, it is certainly very convenient - even more so since the materials are available earlier and don't require as many components as a full fuel or steam system.
Just ran another test, and a stack of coal blocks dropped onto 49 endoflames generates a bit over half a mana pool in 10 minutes or so. With a golem running a 7x7 coal farm, that would work out to like 32 coal blocks per full harvest, and with some sprinklers and an agricarnation, I think I'd still have a surplus.
All that said, my experience with these mods is strictly this modpack, so more science is needed on the BC and RC sides.