Temporary Resolving State on Synchronous HA, is there a way around this?
It's difficult to answer the first part of your question as it seems to be related to the network and/or cluster configuration and not related to the availability mode. You should take a good luck at your cluster logs to see what is the root cause.

1.    Checking  cluster status
a.  Login to failover cluster manager console
b.  Click on the cluster name
c.  Check the summary details for errors 
d.  Click on networks under the cluster name
e.  Check the summary and network connections tab at bottom of the window for errors 
f.  Since this appears to be a 2 node cluster w/file share witness supporting AlwaysON, make sure each node and the FS has a vote in the cluster.

2.    Checking for file share witness errors
a.  Confirm the share is online and available to the network

3.    Obtaining cluster logs
a.  Login to a cluster node as an Administrator
b.  Examine both the System and Application event logs. 
c.  Use powershell commandlet:  get-clusterlog  -uselocaltime ***this will save a cluster.txt file to C:\Windows\Cluster\Reports examine the log

As to your second question regarding patching, I assume that the nodes and the FS each have a vote.  If the secondary node is getting patched (windows patching or SQL SP/CU), the AG on the primary node will be available provided quorum is maintained between the primary node and the file share witness. If quorum is not maintained, the AG will shutdown  in order to protect the databases. The Availability mode is not a factor.