I agree, over reclined and no to the noodles. If the seat pulls to one side it may also be caused by the belts being done up with the lock offs on the seat, or having the seat belt in lock mode. To alter the tilt, try using the tether on the other side to where it currently it, do not use the lock off, or the locked belt. You can use a normal locking clip with the MA if needed. If is it caused by the seat, you may need to try another seating position.
As far as I know, this is
not allowed with the Marathon or other related Britax seats. The OP said the tilt is due to the 'seat grooves' being different on one side; I assume this means something on the vehicle seat that is not symmetrical under the carseat base. In that case, perhaps other seating positions should be explored. If the tilt is exacerbated by tightness in a locking shoulder belt (OP, I'm not sure how you installed... if you used LATCH, all the seatbelt discussion is irrelevant anyway), then using the seat's built-in lockoffs instead may help. A little bit of sideways tilt is not a safety issue, so you could decide to live with it, if it's not enough to make your child sit uncomfortably. If the tilt is enough to be really annoying, and if it is caused by some irregularity of the vehicle seat, you (unfortunately) can't fix it by putting a leveler under the carseat base, as you show in your photo.
I agree that, according to your photo, the seat looks very reclined, and it will tend to get more reclined after you put on the RF tether. To install it somewhat more upright to begin with, just position the carseat base a bit forward of the vehicle seat bight to begin with, before you tighten up your seatbelt or LATCH strap. You may have to experiment a few times to get the recline you want (maybe start with approx. 1" out from the seat bight, and see how that looks when you tighten things up, then move in or out, depending on what angle you need for your child). Good luck!
Oh, and one other thought on the tilt issue. If the problem is caused by the vehicle seat under the carseat, then switching from a seatbelt install to a LATCH install, or vice versa, may be worth trying -- since the carseat base usually sits in a somewhat different position laterally (side-to-side) depending on which install method you choose, you may have a 'friendlier' surface under your carseat if you can shift it a few inches sideways by changing the install method. IIRC, your vehicle is a 2004, so I assume it has LATCH...
Katrin
