I am not a grammar-expert, nevertheless for the (missing) article in Greek I would refer to ANCIENT GREEK GRAMMAR for the Study of the New Testament, Heinrich von Siebenthal, 2019, Par. 133: “Definiteness without the article (↑BR §149.2–5; BDF §252–259; Z §171–183)
I. Certain types of phrases lacking the article may still refer to something definite:
133a 1. This often applies to noun phrases embedded in preposition phrases (↑184–186),
in C[lassic]G[reek] mainly to phrases used as adverbs, in K[oine]G[reek]/NT, however, more generally, e.g.:
ἀπ᾽_ ἀρχῆς from the beginning (1Jn 2:7)
ἐκ _ νεκρῶν from the dead (Ac 17:31)
ἐκ _ χειρὸς ἐχθρῶν from the hand of our enemies (Lk 1:74)
παρὰ _ πατρός from the Father (Jn 1:14)
ὑπὲρ _ ἁγίων for the saints (Ro 8:27)
πρὸς _ κέντρα against the goads (Ac 26:14)
By the way, especially the above cited book of Zerwick, Biblical Greek, Par. 171-183 has some clear comments on the Article. Maybe that will help you.
As for the manuscript-evidence I probably can help:
I consulted the INTF-Transcriptions (
https://ntvmr.uni-muenster.de/collation) for the ms-evidence on επι της γης/επι γης (in the combination with εν (τω) ουρανω / εν (τοις) ουρανοις).
I found 5458 Ms-Lines with επι (της) γης (with and without ουρανος).
επι της γης occurs 5245x, επι γης 213x (less than 4% of all occurences).
In Mt 28:18 (except ms 03*, 03corr, 05, 13, 333, 372, 2680: επι γης), Lk 2:14, Eph 3:15 and Hebr 12:25 επι γης is the main/single reading.
In all other Verses επι της γης is the dominant/single reading, the deviations are mostly very few in numbers, this goes especially for the use without ουρανος.
In Mt 6:10 the mss 1093 and 1582 have επι γης in the firsthand, corrected in επι της γης.
In Lk 11:2 ms 01 has επι γης in firsthand, changed by corrector 2a to επι της γης and re-corrected by the same corrector 2b to επι γης.
It’s remarkable that in most cases εν τω ουρανω/εν τοις ουρανοις combines with επι της γης (exception: 1Cor 8:5: ms 18; Mt 16:19 ms 042 has επι γης), whilst εν ουρανω/εν ουρανοις can be found combined with επι γης as well as with επι της γης.
The article is often used, when γη is used in the concrete meaning (pulling boats ashore, something falling on earth etc).
In the less concrete meaning in Heaven and Earth the use of the article doesn’t make any difference, so that could result in the Verses:
Mt 6:10 (114 mss with επι της γης; 17 mss επι γης)
Mt 28:18 (7 mss επι της γης; 133 mss επι γης),
Lk 11: 2 (4 mss επι της γης; 9 mss επι γης);
Rev. 5:3 (89 mss επι της γης);
not identical, but comparable :
Acts 2:19 (100 mss επι της γης),
1Cor 8:5 (1 ms επι της γης; 7 mss επι γης).
Mt 16:19 (139 mss επι της γης; ms 042 has instead of the second επι της γης the non-articular επι γης).
I think there is no semantical/linguistic difference in the more or less abstract use of heaven and earth between expressions with and without the article.
The articular use of ουρανος seems to lead to an articular use of γη. The non articular use of ουρανος doesn’t lead to an obligatory non-articular γη.