Keep in mind that the number of questions on this site doesn't give any indication of how common such issues are, since people usually only post when something is wrong. We don't hear about all the cases where everything is fine.
I don't know any reason why math advisors should inherently be better people than in any other field, and I don't know of any empirical data that attempts to measure this. However, a few of the specific issues you mention are perhaps less likely to arise in mathematics, due to cultural and structural reasons.
"my advisor has stopped funding me"
In the US, at least, the main avenue of funding for math graduate students is through teaching assistantships, since math departments teach a large number of service courses. Faculty who have grants can sometimes offer their students a research assistantship instead, so that the student doesn't have to teach. But a student really isn't completely reliant on their advisor for funding. Moreover, there typically aren't major expenses for the research itself (no expensive equipment, etc), so as long as the student is getting paid, research can continue.
(This is not necessarily the case in other countries.)
"my advisor wants to be 1st author, when I did the majority of the work!"
The general practice in mathematics is that all authors are listed alphabetically, and the concept of "first authorship" does not exist. As such, people don't bother to keep track of who did the "majority" of the work. So this particular issue doesn't arise in mathematics.
"my advisor is stealing my ideas!"
While individual departments may vary, I think there's a general sense in mathematics that a joint paper "counts" about the same as a solo paper. As such, if a student has contributed to a project, the advisor has no particular incentive not to include them as an author on the paper.
"my advisor wants to add another student to the paper and this is unfair!"
As above, it isn't any particular disadvantage to a student if another student is added.
