MHD's card says a friendly figure within 3 spaces. The wording is not the same as say Gideon who says "another Friendly" figure.

Is this similar to X-wing, in that MHD can use his card on himself, since it doesn't say another friendly?

Yes. Onar can do the same with his "get down" for example.

Good. I am glad we played that correctly.

Perfect, just making sure we read it correctly.

Leia's "Battlefield Leadership" ability got errata'd to "another friendly figure". You can see the change on the alt card of her on the speeder. Just as a comparison of how the wording matters.

Yup. A figure is friendly to itself and within 0 spaces of itself.