Will restarting the “Cluster Service” on the active cluster node cause any outages

When you get a network is partitioned error, it means that the server that is currently running your cluster applications is isolated in some fashion from the other nodes. It is entirely possible (and likely), that you services will continue to run, assuming there are no other faults. The warning is telling you that if a failover were needed, it will likely fail (usually due to the node not having a path to hand off the disks/CSVs).

Be sure to carefully check the network topology and your cluster network settings between the servers in question. We had a nasty experience with this where the failover cluster was using multipath NICs for inter-node comms that were different than the ones SQL server were using (i.e. separate VLANs). Because both the primary and backup cluster connections were pathing in such a way that quorum could be lost if only one switch went down, the SQL server would still show as being online, but the cluster showed partitioned, meaning that if the server (or a switch) were to fail, it would bring the cluster down hard.

Is this to have a file share on the SQL cluster? If you share a drive on node1 then do a failover to node2 the file share will go away unless you define it as a cluster service. There is a resource type simply called File Share in cluster administrator, this way the active node will have the file share (don't use admin file shares). Make this depend on the physical disk and the cluster IP address.