71GTO,
It depends on you. I stake the fig trees that I grow as trees (not bush), till the main trunk is straight enough. After that I remove the stake. Whenever I am in town I check the plastic plant tie to make sure its not harming the trunk, even it stretches.
Eli,
Mix the limestone and slow release fertilizer together. You should also add pine bark mulch in there too, helps with drainage. Your new soil should be similar to your existing soil, or you will have problems with the drainage.
After you added the soil to the bottom of the pot, broadcast some lime and slow release fertilizer on top.
I use Osmocote for all my plants. By looking at the size of your pot (if you are going to keep the plant in the same pot), I would guess that you need to mix, 100-150 grams of limestone and 4 tbs of Osmocote SRF, into your new mix. Then on top broadcast about 100 grams of limestone and 2 tbs of Osmocote.
Before adding the lime you should determine the pH of your existing soil and your new mix.
Also take it easy with liquid fertilizer for the fist month, since your tree has never been fertilized (liquid fertilization) before, it could harm the roots if too much fertilizer given too often. For the first couple of time I would use All purpose MG fertilizer at half strength, after that you can go full strength if you wish.
I've used MG fertilizer on my fig trees in past and I believe half strength of MG would work fine given every two weeks, instead of the full strength.
Navid.