I will try and answer your questions....
1. if you are patching a client directly (ie. not from the cell mgr via an installation server) then you can "cd" to the NFS mount and run the omnisetup.sh against a bundle patch or install an individual DPLNX patch with rpm
2. least component install is DA. To add more components later, best to do so via cell manager and installation server. omnisetup.sh could be used but it might moan about patching levels as you've already install DA and patched it.
3. see the commandline reference doc file which comes with DP....