you cannot blame Allah for what he has promised to do numerous times throughout the Quran.
Yes you can - at the very least you can be disgusted with such a "Divine Plan" for mankind - as it makes no sense (i.e. test) and is cruel and petty. Regardless - it's definitely one of the reasons to reject such a God.
There are plenty of reasons for thinking Allah is a fraud, but i'm sorry to say, the death of a relative is not one of them
True but it raises the question "Why" and Islam (or any religion) cannot provide an adequate response to that.
Why does God need make us suffer pain?
And trust me - anyone who has suffered such pain that life itself is not worth living - that they would rather have never been born - deserves an answer to that question.
I have heard all the answers religion gives. They are all inadequate.
The lack of an adequate response to this question is a very good reason to reject religion/God.