1) It’s common for some Reformed amils to make the following two claims:
i) The church is the new Israel
ii) Christ is the true Israel
But if you combine both claims, that will yield a third claim:
iii) Christ is the true church
Clearly, though, that shows the need to qualify our usage. It doesn’t make much sense to say that Jesus takes the place of the church.
1) There’s a serious exegetical argument to be made for (i). However, that’s somewhat ambiguous, depending on how we define the key terms.
2) Concerning (ii), this only makes sense if we use it as a shorthand expression for corporate solidarity or federal headship. Christ is the true Israel in the sense that Christ represents Israel, not that Christ is identical with Israel.
By the same token, Christ acts on behalf of his people (“the church”). To some degree he acts in their stead, as their redeemer (i.e. vicarious atonement, penal substitution).
However, it’s not an antithetical relationship, as if Jesus supplants the church.