Hi Bo, and welcome to the citrus forum.
I will only comment on one aspect of your post since many others here have more experience with citrus per se. Placing gravel in the bottom of a pot does not improve the drainage in the pot.
When soil is watered, it is first saturated, then some portion of the water drains out by gravity. The amount of water that remains in the soil is what is known in soil science as the "field capacity." When a container is at "field capacity" the adhesive and cohesive properties of water result in a portion of the mix near the bottom of the pot remaining saturated. This is known as the "perched water table." Within the PWT there is no aeration of the roots and root problems develop. The lower the PWT, the better.
The finer the mix, the higher the level of saturation of the medium in the bottom of the pot and the higher the perched water table. The coarser the mix, the lower the perched water table. The nice part about CHC is that they hold a lot of water yet containers of CHC have a neglible perched water table.
Another thing that lowers the PWT is increased height of the container. (That's one reason you see citrus and other trees grown in these 4" x 14" containers.) Gravel in the bottom of a container doesn't effectively contribute to the growing medium space. All gravel does is shorten the effective height of the container and raise the PWT.
I hope this is helpful. Others will comment on this and other aspects of your post.
SB