John: I like your plan except I can't do a whip&tongue on that short of a stub. I've had very good luck with W&T but would need several more inches to work with. Then if the W&T fail, T bud in May on that same stub or a new sprout as soon as the wood turns from green to reddish. I'd do the W&T when the tree first starts to push leaves, probably March where you are. I've had great luck with T budding in May and forcing after 2 weeks if the bud takes. I'd keep more laterals and space them out up and down the trunk. It won't hurt to do two or three of each W&T and the same on budding if needed later. As long as you cut back on all remaining laterals, the tree will be fine starting out with 9-12 branches. Latter select the best of each variety.

I'd plant the trunk straight and have the root, below ground, at an angle. Trim the high side of the roots if needed so that the graft union doesn't set too low. I've done this before and it worked. If the stock is small caliber or if there is a low branch that could become the new trunk, then doing it the other way could work just as well. You won't be able to pull the top straight until after it has rooted for a year. By then it may be too stiff to bend.

Do you know the names of the varieties and the rootstocks? I always start my bare root plants in pots, in good quality potting soil, and have around five apricots growing in pots right now. First, look at the size of the roots, the way they grow, and get a pot which would allow the roots to spread out and down as much as possible. A fifteen gallon plastic pot half filled with soil seems to be better for the plants than trying to cram the roots into a five gallon pot. The larger pots don't dry out as fast as smaller ones, and in our hot summer climates, keeping the pots watered can be a challenge. After a year of so, if the roots start growing out of the holes on the bottom, it's easy just to lift out the root ball in a 15 gallon pot, add 6-12 inches of fresh potting soil on the bottom, two teaspoons of slow release Osmacote fertilizer mixed in, and replace the tree at the top. And it saves buying another pot. You plant the trees in pots the same way you would plant them in the ground, spreading the roots out to their natural level of growth, filling in the potting soil carefully so the roots aren't compacted together. The branches are pruned (or not) to balance the root spread. If the roots are long and ample, the branches need less pruning. If there are a number of long branches that make the tree top heavy, then they can be pruned back by half. The article below will give you more information. Good luck. Here is a link that might be useful: Fruit Trees in Containers

As soon as your ground is not frozen and you can get a shovel in it. The more dormant the tree is the better.