Re: 50 amp cord and types of service
The connector looks like what you need.
For the breaker, yes to style and rating, however, ABYC recommends an interrupting rating of 3000A for a 125V circuit. The Blue Sea you referenced has an interrupting rating of 1500A at 125V. Since you're breaking both the neutral and the hot leg that may be sufficient, I simply can't remember what the code says about that (hope someone else can weigh in on that).
ABYC recommends that the circuit breaker be installed within 10' (wire length) of the inlet connector on the boat. If the daily use breaker is greater than 10' from the inlet they recommend installing a second breaker or fuse within 10'.
[Edit] if you care about meeting ABYC then you might look at Blue Seas "A" series instead of the "C" series, they specifically say they meet ABYC. Looks like you can't get the toggle in a two pole, but some of the other styles do come in two pole. [/Edit]