Wow, I havent seen any of your issues before mbedyn, that cpu utilization is pegged alright.
First off, what kind of hardware are we talking about here?
Secondly, that rule your setting off is in your snort.inc file, not in your rule categories. Apparently this rule has to do with preventing NMap scans of your network.
Go to Diagnostics/Edit File. Load the /usr/local/pkg/snort.inc file and scroll down until you see #sf Portscan. See if you have your sense level set to medium or high. If it is, then edit setting to low, and then press save. While you're there in the snort.inc file, make sure under #Flow and stream, put a # symbol before "preprocessor flow: stats_interval 0 hash 2"
Hit save again and Go to Services/Snort.
Blocked tab - X out any entries, then
Alerts tab - hit clear, then
Settings tab - hit save.