You are wise to study the possible pitfalls that may, and do, sometimes occur and to do due diligence concerning your eventual selection of a broker. But at the end of the day it is a leap of faith as to which one will be safest for you.
But if you spend too much time concentrating on seeking out devils on the walls and ghouls under the bed then you will certainly find some and there are plenty of scaremongers willing to help you with this.
But it is strange how you mention these types of broker issues but, like so many others, ignore the one ogre that will for sure, if you are not careful, rip out your financial intestines and feed them to the market vultures within a few months of your starting your scalping and news straddling - and that ogre is you.
It doesn't take much to read through the tons of postings here how "95%" of new traders fail - but the reasons discussed about why this is are rarely related to the broker. Certainly, there are regularly various posts on specific "scam" instances, but the reasons for traders completely blowing the accounts are almost entirely due to a lack of education, understanding, training, knowledge, awareness, greed, inconsistency, risk mismanagement and so on.These are the areas you should be focusing on.
If you decide to buy a new car and read all the reviews, you will probably not find one mass-market model that does not have some bad reviews, and if you then read all the statistics about accident risks and injury/fatality occurences, you will probably conclude that one should not drive at all. But the best one can do is select the most appropriate car for one's purposes and abilities and then concentrate on developing one's own driving skills and road experience as much as one possibly can - even so the risk of accidents and repairs cannot be entirely eliminated - this is basis risk/consequence analysis.
But if you are really so scared of these risks from your broker then you would do better by forgetting trading and doing something else with your money - and you will probably ,at least statistically, end up better off as well!
...but this thread is now starting to repeat itself and I guess the main meat of this topic has been laid on the table. It is up to you to help yourself to what you fancy....