Have done something similar. You have to do an energy budget with inputs, outputs, and storage.
First, your inputs. 500 watts of panels will produce around 200 AH of 12vdc power each day on average. Little less in winter, and of course cloudy days. Leaving aside the Yamaha alternator, this is your max potential energy input.
Second, your outputs. Refrigeration and freezer are, by far, your greatest consumers. I too went route of custom built boxes with separate fridge. I used isotherm 12v systems with air cooled compressors. Between the two, about 80-100 AH consumption per day. Beware, with 3 inches of insulation, the boxes get pretty small pretty quickly, but that's your call. The Engel boxes are well regarded and probably less expensive than building your own. For ice, I bought a bunch of covered ice cube trays. Adler Barbour also makes an aluminum ice cube tray for their fridge conversions that are great, but expensive. Cubes are pretty big so they last
Cooking. Maybe I missed it, but beyond the BBQ and microwave, not sure how you plan to cook. Microwave does take a lot of energy, but rarely gets used for more than a few minutes. Rough term, it will consume around 1 to 1.5 AH at 12v for each minute of cooking. Other electrical means that are possible with solar are induction hot plates and instant pot cookers, either of which would consume around 30-40 Amps for each hour of cooking (very rough numbers). Personally, if I were in your situation, I would go with a small propane stove and oven to preserve energy. I might also use an instapot because it's so dang convenient.
Other outputs. If you leave any nav electronics on while at anchor such as radar or even VHF, they will be your next biggest energy draw and can easily draw 30+ AH per day. PC and tablet charging also adds up to an easy 20 AH.
In the end, your overall energy consumption will be in the 150-200 AH range. If you keep cooking towards propane. It's actually a pretty healthy amount of power - sailors do it all the time.
Storage - batteries. You're generating 200 AH per day and consuming almost all of it. Because there will be about 6 daylight hours (25%) where you will be running off solar vs batteries, you could minimally size your batteries in the 200 usable AH range which would give you some buffer but not much. I'd probably shoot for at least 250, 300 would be preferable.
Why do I say usable AH? Standard G27-ish sized batteries have roughly 100 AH capacity. Lead acid batteries should not be depleted below 50%. Lithium and Fireflies should not go below 80%. So I'd go 3-4 lithium (240-320 usable AH) or 5-6 lead acid (250-300). Lead acid will last a few seasons under this type of usage. The lithium will last 3x-5x longer. Long range cost will be the same. Lithium will weigh 200 lbs less.
Inverter. Would go with some flavor of pure sine wave 2000 watt.
Its been quite a few years since I tinkered with 12vdc appliances like coffee makers and blenders, but I found them to be severely lacking and expensive. Choices are limited and they were poorly made compared to the highly competitive small home-appliance choices. Go with an inverter and 120vac
Power tools. I do everything with dewalt 20v lithium these days. I splurged for a pair of 5 amp batteries for meaty tasks.
Sounds like a great trip. Very doable with right attitude. You have plenty of power, but do need to be careful about hi-draw consumers like cooking elements.
Peter