A bit late to this question, but another option not listed here: flip your stem.
Most road bike stem aren't a right angle, often they are off by ~6°. This means if you flip your stem then your handle bars will come up and back a bit, this will reduce the reach and hopefully take a bit of pressure off the lower back.
Also you could try rotating the handlebars back, this will have a similar effect. Loosen the bolts of the front of the stem a little, roll them back towards your seated position a degree or two, tighten the bolts back up. EDIT: to be clear, I'm only taking about rotating them back by a few degrees.
I did both of these tweaks to my road bike, plus slid my seat forward a tad, made it much more comfortable. (Yes, I may have bought the wrong size frame, I know, but too expensive to fix it now)