Hello Everyone!!

Welcome Anthony.
Just some random thoughts on your queries:
1. I recognise the Achilles/calf aches you mention. For me, I found a couple of trips to the physio for some good sports massage really helped, plus ice therapy as necessary. Happy to say it's not something that's troubled me ever since.
2. Running in the rain shouldn't cause you too much problem (plus puddles & mud are fun, although the mud can be a bit slippery obviously!).
3. Winter is ok too if you take time to get used to it and always make sure you keep your core warm. But if you feel it's too cold (anything below minus 5C for me) then maybe its better to go to the gym that day! Seriously you don't want to mess with frostbite -it's not nice...
4. I have no idea about the impact of large calf muscles, although instinctively I would assume that they'll make really good 'springs' for the extra load you'll be placing on them and hence be an advantage for you if anything...

Enjoy...

Welcome!

I always have issues with my right achilles. The best thing for it if it's really hurting is just rest and then really keep an eye on your form. You're already doing a lot of good in that area going completely barefoot but I do see one major red flag in what you wrote:

"My form is pretty good according to Ken Bob's book."

Every time I've thought "my form is pretty good" it's bit me right on the ass. Running form is crucial and it can very well be just as complex and challenging to master as any other sport. If you'd been barefoot your whole life that would likely not be the case. But if you've spent your lifetime in shoes you likely, like the rest of us, learned a lot of very bad habits and those are very hard to un-learn.

When we were kids we all learned very well how to do two things on foot: walk and sprint. Running long distances at a controlled, efficient pace is an advanced skill and make no mistake about it. When you go unshod the skin on the bottoms of your feet become the canaries in the coal mine warning you early on of danger so that's why it's superior even to the thinnest minimalist foowear.

As for issues with achilles and calf muscles that is common and some of it unavoidable but too often it's the result of a common over-correction:

https://www.thebarefootrunners.org/entries/stop-worrying-about-the-heel-strike.1273/

If you naturally contact the ground forefoot first that's OK. If you're forcing what people call a "forefoot strike" you're wasting a lot of energy and risking injury.

Good luck and never lose sight of what's most important: have fun!

About running in cold: here in Finland we run in socks in winter. When it's -10C to -20C you just put couple of woolen socks on top of each other and it's fine. If your step is correct they can last very long time.

I've run 2k to 3k totally barefoot in -1C...-3C on asphalt many times this year with no problems, and I'm a newbie. But just on dry pavement - snow and ice would need more adjusting. And cold numbs your soles so you ought to be careful.