+1.Bee.....I do the same. And with this approach my subs are collectively 10dB hotter than the rest of the speakers at -15 on MVC. Reference or preference, who cares? The subs should kick like a wild mustang at my reference volume and shouldn't run out of steam when transients kick in during movie playback.
Your receiver should not void audyssey and DEQ settings if you lower the crossover. I think you didn't run it properly or else it wouldn't cross your speakers this high (200Hz). If they are rated to 110Hz, you should be able to cross them at 120Hz. See Audyssey FAQ.No effect as long as you are using LFE input, which bypasses a sub's internal xo.
Lower your expectations; they are very far fetched. As regards SPL, it's all relative to the listening area and how far you are from the sub. Anyway, reduce 6dB for every meter added to the 1w/1m rating and you will get the required spl at your main listening position for that 1 watt.