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Frequently checking the plant and removing and killing any snails you see is usually the most effective method. Here is more advice on other options:
https://www.gardeningknowhow.com/plant-problems/pests/insects/organic-snail-control.htm
http://ipm.ucanr.edu/PMG/PESTNOTES/pn7427.html

The most effective (though time-consuming) method for a relatively small garden is to check the garden often, hand-remove the caterpillars and kill the ones you find. If you do this regularly, the caterpillar population will usually greatly decrease quickly.

Also, please see this article about caterpillar control:
https://www.gardeningknowhow.com/plant-problems/pests/insects/prevent-caterpillars.htm

If you want to use pesticides, make sure you choose those that are designed to kill caterpillars. It's even better to ID the caterpillars specifically so you can look up info on that specific pest and choose a pesticide that will be effective. A local university extension agent may be able to help, or see this site:
http://lepidoptera.butterflyhouse.com.au/faqs/ident.html

I would advise a soil test to start your garden project.
Your County Extension Office can help you with a soil test for just a few dollars.
Here is a link to help you find your nearest office.
https://www.gardeningknowhow.com/extension-search/

You can also create raised beds to garden in. Raised beds can allow you to bring in soil to create a good growing environment for your plants.

Here are some links with more information.

https://www.gardeningknowhow.com/edible/vegetables/vgen/raised-vegetable-gardens.htm
https://www.gardeningknowhow.com/garden-how-to/soil-fertilizers/best-soil-raised-garden-beds.htm
https://www.gardeningknowhow.com/edible/vegetables/vgen/vegetable-gardening-for-beginners.htm

Depending on the size containers these are in, they wiill dry at different rates. If they are transplanted into, lets say, a 1 gallon container, Then they might survive that long.

I would not recommend this. They will likely dry out before then, so I would suggest having someone do this for you. Just make sure to only water when the top is dry almost completely.

This is best done during the early morning hours, and before the sun comes up. This will keep them from burning from water/sun magnification, and also keeps it from developing a fungal infection from sitting in moisture for too long in the dark.

No, do not use this soil for gardening.

Serious pathogens in the soil can enter the food.