You may find some tips in the 5 year old "recording over firewire" thread, and if you buy AVCNoodle from Steve Toth, you'll get great support and hand-holding from him in his thread here.
I don't have any of the problems you're experiencing with FireRecord--I never have to plug/unplug/restart anything--but then I'm not using a Motorola box or an Intel Mac. I record all my EyeTV (firewire and USB) and firewire captures with a dual G4 MDD in 10.5.8--if I have any "secret" to share about my DVR/PVR back end it's this: I don't let it sleep, everything stays connected and runs 24/7 recording and serving up files around the house. So for me, "FireRecord" never loses contact with my SA 3250--but since I have multiple firewire devices connected to the MDD I do have to go into Preferences > Devices before each and every recording and just make sure the 3250 is selected as my tuner unit. I select it, I get the green checkmark, and I'm good to start my recording.
It doesn't bother me that this is a very manual process with FireRecord because 1) it works, it has always been one of the big advantages of going Mac/OS X versus PC, yes, I still find it amazing that Comcast has been so accommodating all these years and 2) because I rely on EyeTV for the bulk of the HD that I record--I only need firewire for the special things that aren't in the clear, which for me is at most 2-3 shows per week and the occasional HD On Demand movie.
The second secret or tip I might share with you is a general one about Mac home theater: it's a whole lot less frustrating, things will usually work out better, and you'll enjoy your experience more, if once you set a Mac up in the HT, you leave it set up on the network, leave it connected to externals and don't disconnect it, don't dock it and then remove it, and reconnect later, etc. That may or may not be what you're doing with the MBP, but that's just a word to the wise (from someone who has used Mac laptops in the HT for 4 of the past 5 years...leave them in place.)
If you still can't get it to work after all that, try Steve's firewire capture program, and/or consider the Hauppauge HD PVR--both would probably prove more reliable.