For starters, I would get a 2 or 3 gallon food grade bucket from Home Depot and use that as your primary fermenter. That let's you add fruit without losing volume or worrying about running out of space.
About 2Lb of honey and water filled to 1 gallon will get you a 10% mead. A nice target to start with that potentially doesn't need a lot of aging. Adding ~3lb of persimmons to the primary fermenter will bump you to ~12% ABV. Also a nice ABV that will be ready sooner than later.
The fruit in the primary will generally give you a more rounded flavor in place of juice just kind of tacked onto the end by a solely secondary addition. Some fruit, like strawberries are difficult in primary.
Once fermentation is done, I would rack it off the fruits, stabilize the mead, and then do any additional fruit additions to bump up the fruit flavor as you desire. You can then do any added back sweetening to bring it to your preference.
With all of the above, I will say that proper yeast hydration and nutrients will paramount to having a good mead vs something that struggles and needs a lot of time to be ready.
Hope that is enough to take care of your initial questions.
