A1. Don't be pulling the transducer cable so fast, I use an OLD X-40 Lowrance, about 1989 vintage, and have been able to get the adapter cable from Lowrance in Missausage, on Matheson Dr. Call the they will help.
A4. I had a hand held VHF, good for around the harbour, but when you are out there and need help, you just can't beat the 25 watts of the fixed mount radio. Price wise, there's almost no difference. Get a quality antenna, BPS has 8' foot models, along with the stainless mount.