Hi xtrailman
I can't help you with the intermittent BT issue with the Galaxy Y, but I do know (I think!) something about the greyed out message tab. Bluetooth contains a number of separate components that allows one device to talk to another and control separate functions. For SMS messaging to work between the CX-5 and the phone, both devices need to run Bluetooth MAP (Message Access Profile). The CX-5 does, but almost certainly your Nokia and possibly the Galaxy Y do not. Therefore even with a working Bluetooth connection, the message tab stays greyed out on the CX-5, as the phones do not respond to the CX-5 request for message control, because they do not run BT MAP.
From my research into why my Nexus 4 does not work with the messaging tab, I've discovered that Android (which I assume your Galaxy Y runs) does not include MAP as standard, but some phone manufactures add it on themselves, such as HTC have done with the Wildfire S, which works with messaging in my CX-5 - well sort of, as it displays the messages OK, bit from the wrong sender!
Samsung may also have done this to the Galaxy Y, in which case, turning on MAP should be an option on your phone, as it is on the HTC Wildfire S, under Wireless & Networks>Bluetooth Settings> Advanced Settings> Message Access. Perhaps the menu structure is similar on the Galaxy Y ?
Having said all that, even with a fully working Bluetooth MAP connection, I'm not convinced that dealing with sms messages whilst driving is a good plan, so I'm not too bothered that my Nexus 4 doesn't support it.
I sympathise with the intermittent connection though, sorry I can't help with that.