regarding the "sabotaging career" discussion: I think that is pretty common in many marriages, usually it's because you are scared of what a change of the status quo could mean or that you could lose control over your spouse. In this case this didn't happen because letting Iaon work abroad was something that changed the status quo and meant that Alice had less control over him (probably because she was too certain of having him under full control, as I will explain later it's clear that she wasn't supportive of him there)
However, this doesn't mean that she didn't sabotaged his career during their marriage. Often it's more subtle, they decided his project as a couple often for example (which is fine), so certainly when Ioan (if he ever) decided to take a work that Alice wasnt 100 % onboard with she will have not fully supported him then once he took the job, perhaps even did subtle things to unsettle him. That is actual natural, humans like to be proven right.
Obviously the most obvious example are her not getting her jealously under control. Perhaps not necessarily because she couldn't accept that he was the bigger star, but her wanting him to shut down the fan website and the alleged behavior on set (apparently over being jealous of him and Jessica Alba, which she even confirmed herself) are all things that certainly damaged his career even before she started her smear campaign after the break up. I obviously can't know for sure if any of this was ever intention or her simply being inept to put her childish feelings on the back foot for the man she supposedly loved (just like she is unable to do this nowadays for her kids). I suspect it's more the latter because I'm sure she would have loved Ioan to be a A-lister and live the high life, but for Narcs these things have to happen under their conditions.
I think the fact that Ioan's overacting was the most horrendous in Harrow S2+3 and Liar S2 fits to the idea that Alice was very unsupportive during his time abroad (which happened to be also the time she started to make bigger digs about him online) and tried to sabotage it as much as possible mentally. She herself confirmed that Ioan had nervous breakdowns on calls with her during that time and she pretty much tried to get him to come back from Oz in early 2019 when she threatened suicide on twitter (while in one tweet indirectly even blaming his absence for her breakdown), and a year later she did it by threatening divorce. This is also one way to do it, and again, it may not be even fully intentional, but more subconscious for being angry that he took projects so far away, that also meant that she lost control over him.