1. You are absolutely right in pointing out that the term "arousal" is vague and difficult to define. However, I am not sure if the attention theory and the "arousal" or cortical activation theory are really "in conflict" with each other. For example, the cortex is generally in a more activated state during wakefulness, but its excitability also fluctuates phasically and some of these fluctuations might reflect attentional processes. One way to address this question would be to record from the same BF neurons during both attentional tasks and spontaneous sleep-wake cycles to determine their correlates, but I am not aware of any such study.
2. I am a little confused about your interpretation of previous findings on ACh release in different cortical regions. I thought that there is some evidence for a region-specitic increase in ACh release that is relevant to the stimulus condition or the task being performed. This issue is also touched upon by Doug Rasmusson (B5 in his poster), and he might wish to comment. Also, I am wondering why the attention theory would conform better with homogeneous ACh release across cortical regions, than with the opposite. What am I missing here?