Congratulations! [name_m]Little[/name_m] [name_m]Pascal[/name_m] seems pretty adorable. 
I disagree with @tigermama527 - he may not be old enough to know what name will suit him the rest of his life, but I’m sure he’ll grow into his new name, and I’m sure he’s dealt with enough to know whether he wants a new name, and if that’s what he wants, I think his wishes deserve to be respected. [name_m]Just[/name_m] like if you adopted a child who wanted to keep their name–would you change it? I know a lot of adopted kids who have wanted new names, and they are extremely adamant about it. For whatever reason–they associate their old name with loneliness and lack of a family, they want to be seen as more “American” (which their biological name might not be, if they’re from another country), or they just hate their name/have been teased for it, etc. I think it’s great you’re respecting little [name_m]Pascal[/name_m]'s wishes, and I think giving him a couple of options to choose from is pretty great, too. If you do really like [name_m]Pascal[/name_m], maybe keep it as one of the options, but emphasize that he could go by a cool new American nickname, like [name_u]Cal[/name_u] or [name_u]Pax[/name_u].
And then give him two or three more options besides that.
I think [name_u]Jude[/name_u] [name_m]Pascal[/name_m] is really cool, but I also think it’s fine to do something that could give you the nn [name_u]Cal[/name_u] or [name_u]Pax[/name_u], as well. Like [name_m]Calvin[/name_m], [name_m]Callan[/name_m], [name_m]Callum[/name_m], [name_m]Caleb[/name_m], [name_m]Calix[/name_m], [name_m]Callahan[/name_m], [name_m]Calloway[/name_m], [name_m]Caelan[/name_m], [name_m]Patrick[/name_m], [name_u]Paxton[/name_u] (or just [name_u]Pax[/name_u]!), etc. Or just keep [name_m]Pascal[/name_m] as a middle. I like the idea of keeping [name_m]Pascal[/name_m] as a middle, more than going with another [name_u]Cal[/name_u] name, mainly because it keeps his biological name, if he decides he wants to know more about where he came from, or wants to have a closer tie to it. (Besides, [name_m]Pascal[/name_m]'s just really cool!)
I think giving him a variety of options (provided you really like them, too!) would be pretty great. Like [name_m]Pascal[/name_m] [name_u]Jude[/name_u] “[name_u]Pax[/name_u]/[name_u]Cal[/name_u]”, [name_m]Calvin[/name_m] [name_u]Elias[/name_u] “[name_u]Cal[/name_u]”, [name_u]Jude[/name_u] [name_m]Pascal[/name_m], and [name_m]Isaac[/name_m] [name_m]Pascal[/name_m] (or whichever name you like–I’m just throwing stuff out there at this point!). It gives him a variety of options to choose from, and honestly, if you do [name_m]Calvin[/name_m], I think you could honestly still do [name_m]Pascal[/name_m] as a middle–[name_m]Calvin[/name_m] [name_m]Pascal[/name_m] doesn’t sound terrible to me. 
Anyhow. Congratulations on your adoption! [name_m]How[/name_m] exciting! (Also, super jealous over here! [name_m]How[/name_m] I can’t wait to be in your shoes. :))
All the best!