I wasn't really happy for him at all, but I went through the motions anyway.
I wasn't feeling congratulatory at all, but I faked it good.
この場合、次のように言うと良いと思います。
ーI wasn't really happy for him at all, but I went through the motions anyway.
「彼のために嬉しいって気持ちは全くなかったけど、そのふりをしといた」
to go through the motions で「〜するふりをする・義理で〜する」
ーI wasn't feeling congratulatory at all, but I faked it good.
「全然お祝いの気分はなかったけど、うまくそのふりをした」
congratulatory で「祝いの」
to fake で「〜のふりをする」
ご参考まで！
カナダ 
