A: The BIMA version of MIRIAD can handle files up to 2GB. This refers to version 3.x. The current version in this series is 3.1.0. This release is not developed anymore, except for serious bugfixes. The version of MIRIAD that can handle files over 2GB is called the CARMA/MIRIAD release, and will have version numbers 4.x. The current release is 4.0.2. This release also introduced the python interfaces to miriad, and support for WSRT and ATNF calibration, as well as handling SMA data (now under active development).
A: easiest thing to do is probably fool AIPS into thinking it is something it likes: either use fv to change CRVAL3 in the header of the output from fits to +1 (I) before you load it into AIPS, or load it into AIPS as YY and then use PUTH to change the STOKES axis from -6 to +1.
A: yes, see also this page for instructions, although we expect to have the install script understand Mac's once version 4.1.0 arrives (it now mostly works).
A: the short answer is: you cannot. You need to switch to an 8 bit display. Some commercial X servers used to have 8bit pseudo displays available within their 24bit displays, but luckily in Linux it's fairly easy to run two sessions of X and run miriad/tvflag in the 8bit version:
ctrl-alt-F2 # switch to a 2nd console, login there startx -- :1 -depth 8 # start a 2nd X in 8 bit mode ctrl-alt-F7 # switch back to the 24bit display ctrl-alt-F8 # switch back to the 8bit display