The tafsir of 5:43 can you explain the way he explains the grammar of the verse? Does it imply the Jews had the complete Torah?
The verse does not concern the whole Torah but a specific ruling in the Torah which they were trying to evade by asking the Prophet to arbitrate for them. If his arbitration suited them they would accept it but in fact his arbitration confirms the Torah ruling and they will reject it. It is a divine a fortiori argument that if they already reject the Torah which they ostensibly believe in, then how can they truthfully ask you to arbitrate, you in whom they openly disbelieve? As for the corruption of the Torah there are other verses addressing it explicitly.
Imam al-Baydawi said:
⁽And how do they make you judge, the Torah being with them, wherein is the judgment of the One God⁾ is (i) a call for astonishment at their asking, as an arbitrator, one in whom they do not believe, when the case is that the ruling in question is textually stipulated in the Book that is with them; and (ii) a notification that the purpose of their asking for arbitration is not the discovery of truth and the establishment of the sacred Law. Rather, they were only asking thereby something that might be easier for them even if it was not a divine law in their estimation [As revealed in the words, “Let us go to this ‘Prophet’, for he has been sent with lenient laws: if he gives us a ruling other than stoning, we will take it and use it as proof in the divine presence by saying: thus did one of Your Prhets tell us:” narrated from Abū Hurayra by ʿAbd al-Razzāq, Tafsīr and Muṣannaf (7:316 §13330), al-Ṭabarī, al-Wāḥidī (Asbāb), and Abū Dāwūd (Ḥudūd, rajm al-Yahūdiyyayn).].
⁽then they walk away after that?⁾: “then they turn away from your ruling, which concurs with their Book, after arbitration.”
Hajj Gibril Haddad