Connection pools being reset with Error: 18056, Severity: 20, State: 46. & Perfmon Counters not showing
1 - can't say for sure, I'd have to go find a server to dig into myself.

2 - yes, I see this periodically in my environment though we're not on sql 2012 yet on the systems we see this from. You may also want to check this post though State 46 seems to be related to having a specific Database=xxx in the connection string, does that db still exist?

The way my network is set up I suspect it's the network's automatic closing of tcp sessions after being 5 minutes idle that's the issue - neither the db nor the client is closing the session so the connection pool still thinks the connection is open and tries to use it only to find it's not really open anymore. You don't mention how the network between your web servers and db is configured, maybe your case is similar.

Another possibility may be the (old, not sure if ever really resolved, see http://support.microsoft.com/kb/942861) issue about TCP Chimney Offload settings.

3 - My understanding is pooling requires exact string matches, so whitespace and different order of parameters would cause different pools. (If I'm wrong on that, please let me know.)