Well in short I’m worried about my dads behaviours, especially in his new relationship

He is constantly switching from being hateful about her, finding things wrong with her and then too up her ass and in love with her he can’t bare life. These switches wouldn’t be so scary if they weren’t happening so frequently and within literally 5 minuets of themselves in the same sentences...he doesn’t even really seem it’s weird when he does this? Maybe not even notices it?

One example is he for the first time ever broke down in tears on me today about how much he misses her (my dad has only ever cried in front of me like 2-3 times in my whole life and he’s 54) That in itself was a shock, I held and comforted him but they’ve only known and been together for 9 days. Which is probably even weirder. 5mins after this cry break down about how he misses her so much and can’t live without her he’s going off about if she’s doing this or doesn’t want to see him this weekend then it’s done because clearly she doesn’t love him as much as he loves her and all this other shit..can anyone help me understand what this is? Is he okay?