My answer here will borrow from an essay by Michael Heiser (who I see left a comment on the page you linked to):
Variants in Deuteronomy 32.8-9
Sons of Israel
- The Masoretic Text (MT) says בני ישראל, 'sons of Israel'
- 'Several later revisions' of the Septuagint (LXX) say sons of Israel
Angels of God
- 'Most witnesses' of the LXX say αγγελων θεου, 'angels of God', but Heiser says this 'is interpretive' of...
Sons of God
- 'Several other' copies of the LXX say υιων θεου, 'sons of God'
- Qumran text (DSS) 4QDtj says בני אלהים, 'sons of God'
- DSS 4QDtq says בני אל, 'sons of God'
Just from the evidence for Deuteronomy 32.8-9, the 'sons of God' variant seems the most well-attested, being represented by the widest array of independent manuscript traditions.
Another Variant in Deuteronomy 32.43
After surveying hypothetical explanations of how the variants emerged, Heiser points us to another textual variant in Deuteronomy 32.43; this verse has three variants, again divided between the MT, DSS, and LXX versions.
The text in question is made out of bicolons, which are poetic lines that come in pairs, e.g. 'the sea looked and fled | the Jordan turned back' is a bicolon.
The longest variant of Deuteronomy 32.43 is the LXX, which consists of four bicolons:
O heavens, rejoice with him | Bow to him, all sons of the divine
O nations, rejoice with his people | And let all angels of the divine strengthen themselves in him
For he'll avenge the blood of his sons, be vengeful | And wreak vengeance and recompense justice on his foes
Requite those who reject him | And the Lord will cleanse his people's land
The DSS is the same as the LXX, but is missing the second bicolon, and has slightly shorter versions of the third and fourth bicolons:
O heavens, rejoice with him | Bow to him, all divinities
For he'll avenge the blood of his sons | And wreak vengeance on his foes
Requite those who reject him | And will cleanse his people's land
The MT is missing the first bicolon entirely, the second and fourth bicolons are half-missing, and the third bicolon changes 'sons' to 'servants'.
O nations, rejoice his people |
For he'll avenge the blood of his servants | And wreak vengeance on his foes
| And will cleanse his people's land
Summary of the Deuteronomy Evidence
The LXX of Deuteronomy 32.8-9 and 32.43 both include references to 'sons of God' or 'angels of God'.
The DSS of Deuteronomy 32.8-9 and 32.43 both include references to 'sons of God' or 'gods'.
The MT of Deuteronomy 32.8-9 instead refers to 'sons of Israel', and 32.43 completely lacks references to 'sons of God', 'angels of God', or 'gods'.
While the LXX and the DSS are not identical, they still agree that the original reading of Deuteronomy 32.8-9 read 'sons of God'. The MT represents a minority variant of Deuteronomy 32.8-9, that was probably altered intentionally to '"protect God" or correct theology', that is, it was altered intentionally to remove references to divine beings other than YHWH. This is supported by the MT's more overt alterations to Deuteronomy 32.43, where again the LXX and DSS largely agree that it referenced divine beings.
Altogether, the manuscript evidence for Deuteronomy 32 supports the conclusion that 'sons of God' is the original text of 32.8-9.
The 'Bull El' reading mentioned has a major weakness, in that it is an entirely hypothetical reconstruction, found in no existing variants.
(As for 32.43, Heiser implies via Tigay, one of his sources, that the DSS variant represents the closet form to the original text, with the LXX having added material, and the MT having removed and altered material.)
Circumstantial Supporting Evidence
Daniel 10-12 contains an unusual feature, in that it suggests the nations of the earth correspond to angelic figures. These chapters specifically refer to an angelic prince of Persia (10.13,20), a prince of Greece (10.20), and Michael the prince of Israel (10.13,21; 12.1).
The book of Daniel displays an obvious familiarity with an existing 'Law of Moses' (9.11,13), so it may be the author's concept that nations correspond to angels comes from the 'sons of God' reading of Deuteronomy 32.8-9.
Michael S. Heiser, Deuteronomy 32:8 and the Sons of God (2001).