No – It is closer to “Christ is with us: I stand firm”
You want:
*Christus nobiscum: constate *(if, as implied by the “us”, you are exhorting a group to stand firm) or
*Christus nobiscum: consta *(If only one person is being told to stand firm)
You might also use the (jussive) subjunctive mood instead of the imperative: *constemus *(“let us stand firm”), *constetis *(“may you (plural) stand firm”), or *constes *(“may you (singular) stand firm”).
tee