I am a little nervous using my main battery.
And with good reasons, don't want to be left stranded, don't want to use your starter battery as a deep cycle and shorten its life, etc.
How many Wh the fridge will use depends on a number of factors; Outside temp, fridge set temp, how full the fridge is, if the fridge is in the shade or direct sunlight, etc. All of those will affect the duty cycle and how much energy will be needed to keep it going.
But, let's say it's operating at a 50% duty cycle. That's 30Wh. A Jackery 300 has a 293Wh battery but you won't get 100% efficiency, so let's say 90% or 263Wh. 263 / 30 = 8.7 hours before the Jackery 300 is dead with no input. A Jackery 1000 at 1002Wh and 90% efficiency would result in 902 / 30 = 30 hours of runtime before it's dead. A 50% duty cycle isn't unheard of in the middle of a hot summer and I'd rather have too much battery than too little.
I have a 120w Bluetti solar panel and even if the shade with little direct sunlight it's still able to put out around 30w. Even that little amount of solar for 8 hours per day would extend the time until dead to 45 hours assuming it never sees direct sunlight. If you can get 90W for 8 hours that's 720Wh and 30W for 24 hours is...720Wh. With the perfect conditions and starting with enough capacity you could run indefinitely with that. 90+W for 8 hours would require babysitting and direct sunlight for the entire time, though. My 120W Bluetti panel puts out just over 100W in direct sunlight.
Once you have an idea of your power consumption over time and how much power can be used to recharge and for how long you'll get a better idea of what you need to reliably supply power over the course of a trip. If you're nearly depleting a battery every day then that battery isn't going to last, either. Battery cycle count is full battery cycles, so partial discharges take multiple to add up to one full cycle, so the less exercise the battery sees the longer it will last.
Hope this helps!