I have to disagree with your top 3 best things that you can do to improve accuracy. First is to take an honest assessment of your individual shooting style and proficency to see if your accuracy problems are hardware (gun) or software (you) related. If the gun is mechanically capable of shooting to 2 MOA, but you are only capable of shooting 4 MOA, then doing anything to the gun is a poor investment at this point. Go take a class, go buy (load) a bunch of ammo and go out and work on your fundementals. When you can shoot those 2 MOA everytime, then look at what you want to do specifically with your shooting and make the necessary adjustments to your hardware. Who knows, 2 MOA may be acceptable for your desired results.
How do you know if the limitng factor is software or hardware? Get someone else to shoot your weapon, preferably someone who is better at the way you want to shoot then you are. If I'm shooting 4 MOA and Wormy is getting 2 MOA out of my weapon, and Jesse is getting 1.5 MOA out of it, the gun is not the primary issue. If one the other hand, we're all getting about 4 MOA its probably the gun that is the limiting factor, not me. BTW, look at the group size, not the position of the group. Size indicates capability, positioning indicates for whom the sights are regulated.
Jesse - if you were issued, or allowed to add, a real shooting sling to your M-16, then you were in a better unit than I was. We were not issued slings, we were issued carrying straps made of web and later nylon. And we only used those for parades and passing in review at a change of command. The rest of the time, we didn't even have front sling swivels on the rifles since they made so much noise. The only time I got to use a real sling was during a specific course at Ft Bragg. And then only with the M21 that we were using in the course. The other guy that you were teamed with got to carry a standard M14 with, you guessed it, the web carrying strap.
I also agree on the fear factor, I'm not sure that my eyes were even open for the first "real usage" magazine, I'm pretty sure that all I did was add to the noise and confusion of that ambush.
I gave the FF rails from my Stag 2TL to my gunsmith in exchange for him adding the delta ring and other parts necessary to run normal handguards, but I'll keep you in mind for the ones from the new upper.