He had Hogyoku with him whole time during his battle with Shinigamis. Shinigamis never damaged him to the level, that he will need to use it to heal his wounds, but it's very possible that he used it, so that he don't get tired during a battle. So, he didn't use transformation but he did use Hogyoku.
First time he used Hogyoku (on screen) was after his fight with Yamamoto when Ichigo hit him with his GT.
1. Bazz-B is powerful enough to hold both Renji and Rukia at the same time. At least Renji is on the level of senior captain level and probably Rukia too. If Bazz-B is able to beat them both, than I can see him being stronger than Aizen, if not, than he still would be strogner than Base Aizen and probably Shikai Aizen as well.
2. Aizen is stronger than Candice that's for sure, question is: "Will he need KS for her, or will be able to take her down with his base abilities?"
3. Same as above, he is stronger than Bambietta, but he will need his KS for this. Don't forget that Aizen need to try against Shinji, Bambiette one shotted him.
4. As Nodt seems to be pretty strong, so Aizen will need at least KS to defeat him. If Rukia is senior level tier, than I can tell that he would need maybe even his bankai to beat him.