I have to disagree with jean001 a little. New potting soil (looks like yours has some perlite as well) will not compact and/or dry out such that it pulls away from the edge of the pot, and water runs right through without wetting it. Given the size of your pot, and the amount you're watering, I'd say it's been too wet. Avocados like well-drained soil, on the slightly dry side. A new tree, with few roots to absorb and transpire water, doesn't require much. As it grows and water needs increase, it can use more, but easy does it. As jean001 suggested, growing in a pot is MUCH different than in the ground. Care must be taken to maintain the correct soil moisture. There are perhaps a few avocado varieties that will produce in a container, but it would have to be a very large container. Also, you'll get few, if any, fruits, without cross-pollination. If you maintain a drier pot, and keep an eye on moisture levels further down in the mix before watering, it's possible your tree will come back. The way it's looking at the moment, I'd give it about a 30-40% chance. Also, small avocados are prone to sunburn -- don't keep it in direct sun all day. Shade it slightly, and/or paint the trunk. -Bruce

"Black sooty residue" is probably the key here -- I suspect what you have is actually called Black Sooty Mould -- a mould which grows on honeydew, which is the sticky-sweet discharge from sucking insects like scale or aphids. I would look carefully at the branches and undersides of the leaves, I suspect you will find an infestation of either scale insects, mealybugs, aphids, or similar. If so, I would treat the trees, either with an oil-type spray, or with a systemic insecticide like Imadicloprid. Dennis SE Michigan

How much water is it receiving? Looks healthy fo me. Look on underside of yellowing leaves for any black dots, which could indicate the start of a fungal disease called black spot. You can remove those leaves & any fallen leaves below the rose. to prevent the spores from reinfecting the plant. Also apply mulch around your roses. This helps prevent fungal spores found naturally in the soil from splashing upward when it rains or you water. The mulch also acts as a weed block and decreases watering requirements by keeping the soil below moist. Use about a 3” layer. Don’t pile the mulch against the canes either.

Persimmon typically require 3 to 4 years to establish a sturdy root system to support ripening fruit. (Mine, in Long Beach, CA, did exactly that.) And as nil wrote, it's fall now. Time for leaves to fail, look ratty, and drop.