In 28, the dative articles, tois … tois, are demonstrative adjectives modifying verbal adjectives. They effectively identify “the ones” loving God with “the ones” purposefully called, for whose good God works all things. In 29 Paul looks at the beginning and the end of a deliberate process. The foreknowing, in light of 28 and the “gar” (introducing the explanation for 28), is more than a passive, non-purposed acknowledgement. He uses the one pronoun, hous, to cover both “opening batsmen” in a lovingly-purposed process where God’s sights are set on the ultimate glorification of each person making up “those whom” he foreknew and also predestined. In 30, he inserts two steps between the openers and the goal, the calling of 28 and their justification. This time, each hous (which might be seen as a mixed demonstrative-relative pronoun) is treated to its own straight-demonstrative pronoun (toutous), indicating that there are not merely four groups in this verse (there is no singular pronoun for a group) but that the very same individuals are the beneficiaries of each stage from beginning to end. The repeated refrain is “(Those) whom … these”, and not “Of (those) whom … some (or many)”. Note, too, how, with each pair, the “kai” (“also”) requires that the same people are the objects of the two actions. In the light of prior—and ensuing—discussion of suffering of God’s heirs, the message is that in “all things” God’s purpose that all his sons enter their glorious inheritance will not be thwarted.
As for the word order, compare Ro.8:30 with Jn 15:13: Greater (object modifier) love (object) than this has (verb) no-one (subject). The more common Greek word order, of verb, subject, object, modifier, is juggled so that the object and its modifier receive the emphasis. In Ro. 8:30, the placement of the “(those) who” clause adjacent to the antecedent action provides a defining link to “these”, the plural object of the action in the main clause. Compare also Proverbs 3:12 (LXX): “For whom the Lord loves, he disciplines …” In Ro.8:30, in each of the advancing ‘refrains’, the subordinate clause takes precedence. This, the “hous” clause, is either (a) a “whom” clause, a relative clause directly modifying the object in the main clause, “these” (toutous), or (b) a “those whom” clause, a noun clause in apposition to “these” and containing within it an adjectival “who” clause modifying “those”. Either way, the “hous” clause refers back to the ones who are the object of the antecedent divine action.
For example, in the final step, the climax, the subject of the main-clause verb, “glorified”, is “he”, since the verb is 3rd person singular, while the object of “glorified” is “these” (hence the accusative ending). In the subordinate clause, whether we follow (a) or (b), “hous” takes its case (acc.) from its role as the object of “justified”. Following (b), the understood, but unwritten, “those”, or “the ones”, would also be accusative, taking its case from that of “these”, which it is in apposition to.
There is good reason to opt for (b). Firstly, “the ones whom, … these ones” better matches the “tois …, tois” of v28. Secondly, the Greek “hos” is not necessarily always quite the same as the English “who”. Notice in the Proverbs verse cited above how there is no immediate referent for the relative pronoun, “whom”: “that person” or “the one” is missing from this translation. According to Thayers on “hos” (II,6,a, under Strongs 3739) in some cases, a demonstrative pronoun such as ekeinos or houtos is understood as included in the relative, though unwritten—note the “hois” in Matthew 20:23, the “hō” in Luke 7:43 and 47, the “hon” or the “hou” of Romans 10:14, or the “hōn” in Matthew 6:8 and 15:18.
The same merging of relative and demonstrative takes place in the English “what”—“that one which”, or “that thing that”. We don’t have such a word for “he who” or “that person whom”, but a number of translations of Romans 8:30 compensate for that. Instead of the jarring “whom he …,” many translations supply a referent demonstrative pronoun (“those whom”—ESV), or simply give the demonstrative alone and treat it as a relative (“those”—NIV). This leaves us with, “Those whom he justified, these (the same) he also glorified. It would lose too much, but just to explain the case endings, it could be put this way: He also glorified these (the same--accusative), the ones whom (acc.) he justified.