1. Some consultants want ownership of intellectual property. I don't care and it hasn't been a problem for me. You can try to negotiate this. However, it gets more complex because now you have 3 interested parties because it's likely that A wants IP ownership too.
2. I have liability insurance because it's a common customer ask. My insurance company even sends them coverage so they can verify contract terms.
3. This is a shady practice that most recruiters engage in. At worst, it essentially keeps you from working by yourself or with a different umbrella because Umbrella has communicated with every major company in town (or even worse if they're a national or international corporation). I would negotiate this clause and get it narrowed until it only pertained to the specific project and was time boxed. That way, you can work on other projects at A and are free to work with any other company. Ideally, they would drop the restriction altogether, but it depends on how much you want the job.
One more thing that you didn't mention - payment terms. One of the sneaky clauses they add is that they can only pay you if the customer pays them. You want to get that taken out because they will claim they haven't been paid and make you wait. This puts you in a position of weakness on future issues because you'll be concerned about not being paid. If they're reputable, they'll pay you, though it might be good to ask around for other people who have worked with them if you can. My situation was that Umbrella subcontracted me to a 3rd party recruiter who tried not to pay me because Umbrella didn't pay them, which is by design. Fortunately, I had already negotiated the conditional payment clauses out of the contract with well-defined payment terms. When 3rd party tried not to pay me, I evoked the contract and they paid me.
Good luck.