To me it seems that the subject of δῆλον is everything in the sentence except for Ἄνδρες στρατιῶται and δῆλον itself. The phrase τὰ…Κύρου is the subject of οὕτως ἔχει πρὸς ἡμᾶς.
δῆλον ὅτι is sometimes written δηλονότι. Although it could be analyzed as an impersonal expression, δῆλόν [ἐστιν] ὅτι followed by a subordinate clause, it functions more or less like an adverb, “clearly”. Usually, as here, δῆλον ὅτι/δηλονότι doesn’t precede the ὅτι clause, but instead is inserted as the second element or later, so the word order suggests that it should be analyzed as an adverb or a parenthetical expression, not as a main (non-subordinate) clause followed by a subordinate clause.
Since subordinate clauses introduced by ὅτι in Greek generally take a nominative subject and a finite verb, a clause with δῆλον ὅτι/δηλονότι is generally indistinguishable from a main clause modified by an adverb.
I agree with Barry: πρὸς ἡμᾶς is predicative. τὰ Κύρου is the subject. I think (1) πρὸς ἡμᾶς is too far separated from τὰ Κύρου to be part of the noun phrase, (2) it follows the verb, ἔχει, and (3) if πρὸς ἡμᾶς were part of the noun phrase with τὰ Κύρου, we would expect τὰ Κύρου . . . τὰ πρὸς ἡμᾶς.
But I think M&H’s translation, “the relation of Cyrus to us” would be ok because English would need to supply a noun to translate τὰ Κύρου.