If you've not owned an Amur maple before, you should know they are notorious for dying back SIGNIFICANTLY at cut sites. Hard pruning a branch can result in a huge scar that rots out. They can also be prone (especially older ones like this) to rotted trunks at ground level...I've had (and still have) amurs with this issue. This is germane because apex regeneration is a constant battle with these. The top shoots get too thick to quickly requiring constant hard pruning to keep them from outgrowing their tops. You have to replace, or completely reconfigure, the apex in these trees every few years...
Also, leaf reduction is not as dramatic as say, trident maple, but it's OK. I have never leaf pruned mine, as I'm wary of the dieback issue. I keep them in full sun. Leaves tend to be just over an inch long. Some are shorter.
They're fun trees to work with and pretty vigorous growers and EXTREMELY cold hardy. I simply leave mine out with no protection. They've seen temps down to 0 F and had no problems. Coddled with with mulch and a windbreak, mine begin growing in early February... I stopped giving them that and they hold off until late Feb.