You didn't say where you lived. In sand, too much drainage can be a problem. I plant at a cabin on the Oregon Coast and until I put in organic material into the hole, the trees died of thirst in the summer. With the plum tree, I would add compost at planting and periodically mulch with it from time to time.
John S
PDX OR

“…and at some point below that, if it's relevant, is the underground parking garage.”

That’s interesting. I wonder how deep..? Guess in your hole-digging process you could attempt to find out

“So ... I will add compost, manure, fertilizer (organic?),”

As mentioned, the bigger the better… especially if you’re adding soil. “Organic’s” up to you… though it generally breaks down slower; you may want something a bit faster acting. ...but with all that sand, it might wash out quick -- how about a blend of both?

Getting (and keeping) the grass back is also important. Grass will constantly compete for water and nutrients - and always get them first! I can’t really recommend a size… though bigger seems better.

Just keep in mind, the roots will seek what they need, as long as they have the strength. Most fruit tree roots stay pretty close to the surface, finding the soil richer and moisture closer.

…Been a long time since I’ve been to Vancouver, BC. Much like ‘us,’ I believe Saanichton fuzzy kiwi’s are from Vancouver, BC… you haven’t any of them crawling around, do you..? Couldn’t recommend them in tight quarters, but I’ve got some well established vines. When I read they were doing well in BC I figured they’d make it on my rural hillside, too. Here you go:

“Saanichton fuzzy kiwi: Similar to the fuzzy kiwi that you buy in the store. However, it is more winter hardy (to about 5 degrees F) and it is successfully grown from California to as far north as Vancouver, Canada, since it ripens a couple of weeks before the variety Hayward. It is a large sweet fruit, heavily productive and easy to peel.” …Maybe I shouldn’t have gotten started, but I’m still eating them from the refrigerator, daily, and can never recommend them enough.

Good planting – and if you hit that parking garages roof – do tell

“Thanks again for the tips. Now I just have to dig that damn hole... D.”

Just wait for the ground to thaw " title="Wink" />

…and before further envy, you should see my ‘lawn,’ not yet touched this year, some (the fertile) places are nearly a foot deep! …if a couple of acres worth, and easily a four hour job on a riding mower - not counting trimming with a straight-shafted ‘weed-eater’ and walk-behind mower. …It will have me envying those with manageable plots in no time! Throw in a multitude of animal intrusives and sometimes it's nearly too much. At least for those with the fruit addiction, a smaller lot keeps us in check, as larger ones may likely kill us

Mine have leafed out, but where do you live? That's a big factor.
JohnS
PDX OR

Well, the bulk of my mowing is done… my ground's fertility fluctuates so much, to make it worth mowing everything - I wait until the poorest soil areas are high enough --- by which time the rich ground is mighty thick! But a Sears ‘lawn tractor’ did the trick (and about 4 hours)!

Don’t panic, or obsess over your fig! I’m glad you’ve got one. Mine have just begun to break bud at their very tips, nothing close to ‘leaves.’ My Kiwi, on the other hand, have been putting out leaves for 2 or 3 weeks… Scary We had a ‘local frost’ last week … but where I’m at, nothing(!). Frost generally settles on the valley floors, just a ways up into the hills the air apparently moves, or drains down (like water) and it can be much safer. All of the surrounding vineyards are on hillsides, partially for that reason, the other being it’s clay soil is far cheaper.

I’m curious how cold it got ‘up there’ last winter? I don’t remember extreme cold around here, but I’ll never forget our 30 inch snow total! … which reminds me… I wonder if it’s a burn day, I’ve a pile of fir limbs " title="Wink" />