Ranong is dead easy. Yes, you park but they have a nice parking lot there and the boat ride is scenic and short. There is nothing to do in Kawthaung, what the Thais all call "Koh Song" for some reason. It's a dump. So do your border dash and come back to Ranong and enjoy yourself. The "long tail thing" is certainly not sketchy. I've done it hundreds of times (not for visa but to visit the islands beyond it.)
It's also nice then to add a few days on to Koh Phayam and the drive through Isthmus Kra past Chumphon is one of the prettiest drives in southern Thailand. It follows the second "death railway" that was built to bring supplies from the Gulf to the Andaman Sea. Later torn up by the British. Ranong is a nice little border town, lots of good food, a nice downtown backpacker area with guesthouses and restaurants. Lots of hotels. I don't know where you're driving from but if you haven't been south, now is your chance.
Sounds about right, if you, the sender, told the bank to pay all fees, then 500 baht on each end is standard. As others have said, use Wise next time or Western Union.