Hey Argon, I'm very exited to hear you got yourself into a boat that you like. For what it's worth, I think you made the right choice. Yes, your skills will get better but if the "Marvel" is annoyingly hard to track now, you might get better at controlling it but the annoyance will always remain. Alternatively, your skills will develop just as much in the Pungo too but it will become "more fun" as opposed to "finally acceptable". Besides, now that you have made your purchase and are happy, I feel better in telling you that old school kayakers call those Marvel style boats, "Wormchuckers."
For your questions.
The term "paddlefloat" almost always refers to a re-entry tool. Almost all paddles you will find will float on their own. A paddles strap that attaches to your boat or lifejacket is a nice gizmo though. Then you can have both hands free for something and not see it float away.
Here is a great instructional video on how to use a paddlefloat.
Paddlefloat self-rescue Notice it takes him a while to blow it up. You can buy a permanently ready, foam version. It is likely too bulky to store handily in the cockpit so you have to strap it to your deck but if you are in water cold enough to make every second count, it is recommended. I own both and take the foam one in the early and late seasons.
If you have room for a blow up floatation bag (or "sea sock") in the front without making yourself uncomfortable it can, as you say, be a good idea to increase flotation in the event you capsize. While I wouldn't consider it essential because at least your stern has a sealed bulkhead, it does also have the added benefit of reducing the amount of water you have to pump out of a capsized boat afterward. Just be sure to fasten it to the inside with a strap or carabiner. Nothing worse then watching your gear float away.
A throw bag is not much more than a line stuffed into a bag. The obvious advantage is storage. You don't end up with loose rope tangling everywhere and the bag is normally made to clip securely to your boat within reach somewhere under or above deck. Don't ask me how, but when you basically just stuff the rope into this magic bag, it never comes out tangled. The biggest benefit is that while you hold on to the end of the rope coming out the bag's opening, you throw the bag itself and let the rope uncoil out of it while in flight. The added weight of the bag and the rope enables you to throw it much, much further and much more accurately than just a length of rope. Especially in a bit of wind.
Again, Youtube explains better. Although this guy is standing on the shoreline and you won't be worrying about what "style" of throw to use out on a kayak.
Throw Bags One of many Edits:
Here is a good example of an assisted rescue that you will likely learn on your course Saturday. The comment section make some valid critiques but it is still a good demonstration video.
T-Rescue My comment would have been that once you learn it, begin to practice it in rough water. Waves add a whole new dynamic to the practice required and besides, how often will you flip in calm water?
