Can you tell your absolute speed in space?
Yes. You just look at the CMBR dipole anisotropy. This tells you how fast you're going relative to the universe, and that's as absolute as it gets.
"From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 627±22 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 276°±3° , b = 30°±3°"
Note that this doesn't constitute an absolute frame in the strict sense, in that you can't tell how fast you're going if you're in a box. But all you have to do is look out of the window, and you see a blueshift in the direction you're headed, and a redshift in the other direction. Have a look at this question and ghoppe's answer which refers to Douglas Scott who says this:
"However, the crucial assumption of Einstein's theory is not that there are no special frames, but that there are no special frames where the laws of physics are different. There clearly is a frame where the CMB is at rest, and so this is, in some sense, the rest frame of the Universe. "
Normally in relativity your speed can only be known relative to another object
Yes, the cosmic background radiation. Or if you prefer, the universe.
given that as one approaches light speed more energy is required to accelerate faster, based on the energy consumption profile you would be able to calculate at what % of the speed of light you were going?
If you were in something like a rocket in gravity-free space, you could calculate the increase in your speed based upon how much fuel you'd burned. But it isn't a great way to find out how fast you're going. You'd be better off looking out the window at the CMB.
now since you know your own speed, you also know the absolute speed of any other object you encounter from the relative difference following on from this, if you knew your speed you could slow your ship down by the exact speed you knew yourself to be going and be truly at rest, with respect to the reference frame of the universe
Yep. Slow down by about 627 km/s and there's no CMB dipole anisotropy. You are at rest with respect to the reference frame of the universe.
my question is am I right? it seems counter intuitive to derive seeming absolutes in in a relativistic universe
Yes, you're right. I say this as a relativity guy. Some people will tell you there's no such thing as absolute motion, only relative motion. But all we're talking about is motion relative to the universe. Which is as absolute as it gets.