The fig and papaya plants have gone dormant and it's been colder this winter for longer than usual, but once the weather warms up I have no doubt that all of my plants will take off.
Most fruit tree seedlings you can buy are cuttings because most fruit are not true to seed, meaning the fruit dont take the parent-plants characteristics necessarily, which could result in a fruit that is not nice. Usually fruit trees grown from seed are grafted because of that. So by growing a cutting, you'll at least get tasty mangos eventually :)
You said your fig lost a lot of leaves in the winter? If the shoots completely ligninified in tandem with the leaf drop, then your fig likely just tried to go dormant. After all, ficus carica is naturally deciduous.
I was just thinking have you considered cutting plants back and occasionally cut roots away like a Bonsai plant in order to keep all your plants in the same planter. Open cans of beer will attract and drown a few of your insects, possibly a low planter dedicated for your snails and slugs. I don't know much about the gnats that you have but I occasionally hang yellow plastic cards with a sticky substance to catch white flies.
Possible solution is soft tie plant to 1 gallon water jugs filled with rocks, tap water or soil until you decide on alternate plan. Larger planter or possibly square plastic planter if you can find one. By the way, is the plant root bound in the planter?