SQL Server – Change IP Address of Secondary Replica Node in AlwaysON Availability Groups

My question is: - Do i have to schedule the jobs at primary replica and then disable them until fail-over occurs and then manually enable jobs or what is the best way to deal with these please?

No, you should just add a check with the new function sys.fn_hadr_backup_is_preferred_replica

if sys.fn_hadr_backup_is_preferred_replica('your db name') <> 1
begin
    print 'This is not preferred backup replica .....'
        -- If this is not the preferred replica, exit (without error).
end
else
begin
    print 'This is the preferred replica .. continue with backup'
        -- If this is the preferred replica, continue to do the backup.
        -- here goes the backup command .....
end

Alternatively, you can use SQL Server Maintenance Solution - by Ola hallengren which supports AlwaysON as well.

How would one approach this?

With a whole bunch of pre-move work :)

My initial thoughts are: /snipped for brevity

You have the right ideas, let me add a few more.

Pre-Work

• The cluster is now Multisubnet, we'll need to add an IP for the cluster name in the second subnet. This will be added to the cluster name resource as an 'OR' dependency as you've stated above. This can be added at any time (I'd add it pre-move). The cluster CAP will now have 2 IP addresses, one for each subnet.
• Firewall rules, etc.
• The listener (as you've already stated) will become multi-subnet. Another IP address will need to be added in the 'OR' dependency.
• Double check the setting of the client access point (CAP [aka VNN, aka network name]) for: HostRecordTTL and RegisterAllProvidersIP to make sure they are setup the way you want them. Note that you may want to use multiple listeners to facilitate clients that use older connection libraries not supporting the new keywords.
• Decide if you want to remove the replica from the AG (if it's going to take a while to physically move the server) or to just pause the AG. If the AG is removed, the databases will go back into a "restoring..." state and you'll be able to catch them up with restores at a later point after the server arrives and is setup.
• Quorum: There isn't much to say here, it's a 2 node cluster with 1 node getting airline miles. Included because we'll hit this later and it's a common question.

Post-Work

• The server should (with a new IP and proper firewall rules) be able to contact the cluster and join.
• Run cluster validation wizard. Save this report as the initial move report. We may need to look at it later. This will also verify most cluster related items and runs very quickly.
• Verify network latency. Set CrossSubnetDelay and CrossSubnetThreshold appropriately for the latency and health of the connection. No changes may be needed but it's good to double and triple check.
• Restore transaction logs/diffs/etc.
• Add the replica back into the AG
• Revisit Quorum. Even though there are just two nodes in the cluster, we'll want to double check we're not using a disk witness. Depending on the version of Windows we should/could use either a fileshare witness or Azure witness.

There may be additional items specific to your environment but that should be the gist of it. You've pretty much hit the nail on the head in your original question/post, this just adds in a little filler :)