What is the ruling concerning my Hajj, which I performed while in a state of ritual impurity (janabah) due to masturbation, and I was unable to perform ghusl before the tawaf? And does not completing the tawaf al-ifadah render my Hajj invalid? What are the consequences for me?

If you were able to perform ghusl (ritual bath) and ensured water reached your entire body, and then performed the Ifadah circumambulation (Tawaf al-Ifadah) during your second Hajj, then your Hajj is valid, and there is nothing upon you. However, if you were unable to perform ghusl or did not complete the Ifadah circumambulation, then you did not exit the state of ihram completely (second tahallul), and consequently, your ihram for the subsequent Hajj was not valid because you were still in the state of ihram from the previous Hajj.

If you performed Umrah between the two Hajj pilgrimages, then your ihram for that Umrah was not valid. Instead, your circumambulation and striving (sa'i) during that Umrah counted towards the circumambulation and striving of Hajj. If striving was not obligatory for you in Hajj, but only the Ifadah circumambulation, then your Umrah circumambulation counted for it, and your striving was in vain.

Al-Shafi'i mentioned that whoever performs Umrah while still in ihram from his Hajj has no Umrah, because his ihram for it was at a time when he was not permitted to enter ihram.

In summary: The first valid circumambulation you performed around the Kaaba counts sufficiently as the Ifadah circumambulation. Every ihram you subsequently entered for Hajj or Umrah after this would be valid and sufficient.