The Ulti line makes a difference, without a doubt, but if you look at my own post history here you will see I praised the PSL several times in the past for how they handle issues. My wife and parents are all Plat only, and their interactions with the PSL have always yielded good results too. Also, the Ulti line is not 24/7; when it is closed or if their lines are busy, the PSL handles issues. The PSL you contact, however, is also different in each market so perhaps that has something to do with the difference in experience.

I know first hand how irritating cancelations in general are, but three cancelations in 8 days would definitely not be a pleasant experience. Even if they are all tech issues, it makes the whole experience not one to cherish. In those circumstances I usually find myself reminding my own self that tech issues do happen, can sometimes be unpredictable, and I'd rather not be in the air but on the ground when one happens.

So the front-line PSL agent sometimes might not have the ability to just sign off on giving you a non-partner airline rebooking. Sometimes it might be due to policy restrictions that are not so obvious to the customer (e.g. flights that overfly Russia cannot be used for rebooking). There is an interesting thread here on FT that goes over their official rebooking policy. There are some limitations related to fare rules that do apply, which might be what you got caught out with. One strategy that might work sometimes to push the agent on the phone to speak to a supervisor to make an exception, is to politely remind them that keeping you on the ground will open you up for compensations, which can be expensive for AFKL and that given the amount you fly with them (they have access to your flight booking history and future bookings) that you're only asking for the exception because you really need to be there for something important. Polite insistence is the key; and it can lead to creative problem solving within reason.

One thing worth noting here is that AFKL are always responsible for duty of care in these situations. So reasonable expenses, including hotels (if necessitated), has to be refunded by them. If they are putting up a fight for this, I suggest filing a written complaint and claim. Then pushing there for a resolution. While the PSL can file complaints for you, they're actually not the team that deals with these or compensation requests. Calling them only leads to them potentially adding notes, but the other departments are still the ones that need to deal with it. This is why I recommend that you open a written complaint and chase it up that way.

Since these were all tech issues, you should be eligible for EC261 compensation as well, depending on how much delay you had on arrival. The SFO-CDG route is one I have not really flown, but if your delay on final arrival was at least 4hrs, they owe you money for that as well. If your rebooking caused you to still arrive late, then also they owe you compensation under EC261. The final arrival time is what matters here.

Another thing that I'd add is, while most of the ground staff in CDG tends to try and do the right thing, with flights that are delayed/cancelled they tend to get overwhelmed by a lot of angry passengers. They cannot do much more than what customer service will do for you anyway, or the PSL in case you are looking for a rebooking. So my suggestion would be to avoid trying to find a supervisor on ground, and either speak to the PSL for rebooking or file an online complaint via the website to deal with compensation issues.

This really is an unfortunate one. But yes, if they have already boarded and they keep you in the aircraft at the gate, then de-boarding can be a problem. If it is before boarding happened, they can offload you relatively easy but post boarding this is usually not so easy due to the flight manifest being closed and potentially opening up a security issue. In a weird situation like this, I think I would have just gone to the VS flight given the strange status of the flight, but maybe given the day I wouldn't have. Benefit of hindsight does nothing to save you from the delay you had, but once you boarded there was not much they could have done for you unless the passengers would have been de-boarded.

I honestly hope you have better experiences ahead. Flying is stressful anyhow, and things going wrong doesn't make it easier. But it feels like this was definitely a combination of bad luck, situations with not a lot of options, and the PSL itself not having control over complaints/reimbursements.

If you need any specific help related to filing your complaints, feel free to PM me. I'd be happy to give you pointers.