There is a good source of information on cold water safety: The National Center for Cold water Safety at http://www.coldwatersafety.org/nccwsRules3.html by Moulton Avery. And here is a live presentation given to the Chesapeake Paddlers Association a few years ago https://www.facebook.com/CPAKayaker/videos/10151408664486865/ . It is in four parts. CPA offers this free course every year or two. It was just run a few weeks ago.
I totally agree that a wet suit is not adequate for the temperatures you describe, especially the lighter weight wet suits that are suitable for kayaking. I’ve worn wet suits, before dry suits were common, for oyster and salvage diving in the Chesapeake with water temperatures in the upper 30s to lower 40s, but those were very heavy wet suits that were not at all suitable for kayaking. They are too stiff and assume a different body position. I would not trust a full wet suit designed tor kayaking much below 55F water temperature.
I also agree that the 120 rule, or some other total of air and water temperature, has been totally discredited years ago, but it doesn’t seem to want to die. The ACA is largely to blame for this. When you are in the water the air temperature is totally irrelevant.
There are other considerations as far as cold water safety. If you capsize in cold water, how quickly can you get back in your boat in the conditions that caused you to capsize? If you do not drown immediately from the gasp reflex, time is the enemy. Muscle coordination is the first to go. From personal experience in 45F water, I lost the use of my hands in less than 10 minutes without gloves. Can you do a self rescue with gloves on? It can be harder with heavy gloves. Do you have a means of summoning help if you can’t get back in your boat or lose it? There aren’t many other boats out there in the winter.
Always field test your cold water gear. Walk into the water when it is at the temperature you were planning on paddling in. Is it warm enough. If a dry suit, does it leak. If you ended up in the water, how long could you stay there without the temperature becoming a problem. It might be a lot less than you think and you might be in the water for far longer than you think. The USCG has estimated that for an open water rescue, the average response time can be over an hour depending on your location and how long it takes to find you.
I’ve been paddling for over 20 years, a fair amount of time solo, but I’d never paddle in cold water with out the proper gear, no matter how protected or calm the water or how short a time I planned on being out. I also would not paddle solo in cold water but only with other people properly equipped and skilled in rescues.
As far as thinking that your chances of capsizing are about the same as being hit by lightning, people are killed by lightning all the time. No one plans on capsizing, but it only takes a second of inattention no matter how skilled you are.
Another safety note always wear a PFD. At the very least, it saves a lot of public money in recovering the body. And finally, for the average sea kayak, a spray skirt is an essential part of a sea kayak, not an optional accessory. It doesn’t take much to swamp a sea kayak, and without it performing an assisted rescue might well put you in the water too. It only takes a few inches of water sloshing about in your kayak to make it very unstable.