Well, you can determine how much honey to use based on the advertised ethanol tolerance of your yeast. Let's say you do use 71B; its tolerance is 14% ABV per Lallemand's reference chart. All you need to do is to shoot for a starting gravity that will allow the yeast to produce 14% before it poops out, that leaves you with the amount of residual sugar that you desire. If you want medium dry, then you're probably looking at a finishing gravity of around 1.002 to 1.000. Keep in mind that honey sugars are 100% fermentable and there's not much else in honey that will appreciably affect the gravity in a mead must, so a typical bone-dry finishing gravity is on the order of 0.998 to 0.996. Even 1.000 implies that a little residual sugar has been left. So, you can be very analytical about it and use the Mead calculator (or any other handy tool that relates gravity to potential ethanol content, including reading it directly off of your hydrometer scale) to see that you need a starting gravity of 1.107 to achieve 14% ethanol production by the time the final gravity falls to 1.000. For a 5 gallon batch (that is, to mix to almost exactly 5 gallons) you'll need slightly more than 15 lbs of honey to get to that starting gravity. I like to point out here that I am always very analytical, but a good friend of mine keeps reminding me that analytical and anal come from the same Latin root! ;D
Or, you can use Wrathwilde's handy rule of thumb to get approximately to where you need to be. Wrathwilde's figured out that for the range of gravities that mead musts usually start at, 1 lb of honey (mixed in a total volume 5 gallon batch) yields approximately 1% ABV when fermented completely out. So, for a bone-dry finish in your 5 gallon batch, using 71B as your yeast, you'll need 14 lbs of honey according to his method. For a slightly more residual sugar, you'd use a little more honey.
So, you''ll need somewhere between 14 and 15 lbs of honey to achieve a starting gravity of 1.107. I'd start by mixing up the 14 lbs, then slowly adding additional honey until I got the must up to my target starting gravity.
It is harder for me to comment on how much fruit or spice additions to use in a recipe, because that is going to be highly dependent on your personal taste. That said, I think that one orange per gallon will be enough to make its presence known, so yeah, 5 oranges should be enough to establish "orange" as one of the flavor components in your result and it is consistent with Joe's original recipe. With the spices, I tend to go easy on spice additions in primary, and then taste when racking to secondary to see if I'm happy with the result keeping in mind that the spice presence will fade some as the mead ages. If I'd like a little more spice in the mix I'll then add more in secondary, but I'll put them in a steeping bag to allow me to pull out the spices when I've determined that enough flavor has been imparted to the mead. To be consistent with Joe's original fruit to spice ratio, one stick and one clove per gallon is sufficient, but keep in mind that if you're going for medium dry, then you'll finish drier than most JAOs do, and the spices will be more prominent in the flavor profile.
One final suggestion. 71B is a great yeast, and a good choice for this recipe, but it does not do well for sur-lie aging. So be sure to rack carefully out of primary as soon as fermentation is over, and leave all those lees behind. Rack again as soon as the mead fully clears, leaving the fine lees behind. Don't let your mead sit on 71B lees for more than a month or so.