I think not all sports gambling can be consider as fixed. I am playing sports gambling for a long long time. even my more interest is in sports gambling, for most of the time I found sports gambling very fair and even make a lot of money from it. Therefore I do not think that sports gambling are always fixed.
Same as me, till now i have not faced such an issue like games being fixed.
I would just called them rather rigid.
yes, because sports gambling only relies on guess scores or the team we rely on. To win a match in a gambling sport really depends only on luck, although in other gambling games it depends on the same thing based on luck, but in sports gambling, we play not rely on special skills but only do research on the chosen team.