Re: My new toy.
Recommendation if you want an easy motor for a small boat... try a trolling motor. You'd have to really secure the battery (aka capsize problem), but they are more tolerant of getting wet.
Baby bob, is what I recommend for the mast head (float)... if you can't do that, or it's too big, try, putting a swim noodle inside the mast and then spray foam the head of the mast (not to make it waterproof, but more watertight, when the mast fills with water, it becomes ballast when you you turn turtle)...
Yes ease the mainsheet early... My brother refers to it as "sunfishing" meaning, keep the sheet uncleated and always in hand (the base design of a sunfish has no cleat for the mainsheet). It's hard on the hands at first, but you get used to it after a bit... eventually you know when/how to release quickly.
It sounds like you went from close hauled to beam reach without letting sheet out, in any amount of blow that could really roll you over... what's worse when you are "sailing deeper" like that, rounding toward the wind (to luff up) with baggy(er) sails you'll heel harder because you are working your lower surfaces (centerboard) in tandem with the pressure of the wind, in effect making it heel more. Without a corresponding release of pressure on the sails (letting the main sheet out), you're going swimming.
So lets look at the situation...
you were trying to come back to "dock."
Avoiding bobbing fishermen.
So your approach should be (if you can) to finish your docking "into the wind," or as close to it as you can.
So approach from 90 degrees or better off the wind direction (again if you can)... to the dock, hopefully with the boom on the opposite side of where you dock... Example, if your dock/finger is on starboard, then approach on a starboard tack... That way there's no sail in your way docking.
Also again, if you can turn up at the last minute into the wind and against your dock, that is ideal. That way you aren't going to bother with dropping sails, you're likely just going to "flap like mad" once you get back.... Sail right up to the dock easing sheet to slow down, until you release and let flap... once you are alongside the dock, you can secure the boat, and drop the sails (release halyards)... This is a real PITA if you approach your dock downwind... Then YOU WILL Need to drop sails approaching, and your timing has to be perfect, because it's hard to get a second chance if you screw a downwind docking up (you're either paddling backwards the last several feet, or repairing fiberglass!).
By the way, in a pinch (without spending a dime)... if the boat goes over, and you don't have a baby-bob, or noodle in the mast... as soon as you splash, you can swim out to the end of the mast, and put a lifejacket under the top of the mast. It'll get you precious time to right the boat, and even if it's not secured, a great way to practice your Man Overboard drills after you right your boat, and a sail away (with lifejacket floating in the water).
Other thoughts... Sometimes you won't have stinkpotters to help... if you get turtled (boat totally upside down) like it sounds you were... you can sometimes grab a halyard (uncleated)... and swim around the boat, dragging it over the hull, since it' goes to the top of the mast, you can yank on the halyard while pulling down (climbing onto) on the centerboard, and between those 2 things right the boat, at least enough to get that life jacket under the mast head.
Ok, this is a tough, one, and one I never was good at... when you feel the boat going over, climb over the high side, if your timing is good, you can get right out onto the centerboard, before she goes completely over. REALLY good timing, and you can drop over the side, bounce off the centerboard, and back into the boat... I've been known to release mainsheet, and body slam the high side of a boat to flatten it, but then I'm so big, I usually outweigh the hull of these smaller dinghies. This fat man can jump (if he's avoiding swimming). I got tired of sailing like that, so I moved up to a keel boat.
Dinghy sailing can be a blast, but it's also a harsh teacher.. with a couple "tricks," you'll be pushing it JUST to get wet. By the way, life jacket for you until you get a few more miles under your belt, um, K? Also good idea to keep the wife and or Significant other away from the boat until you get a better handle on things, no need to turn her off to sailing (just yet).
You have the right attitude! Keep us posted on your progress.
"Rum Line" a 1982, S2 7.9 - Production boat limit tester, blue-water bucket owner, with wine taste on a beer budget.