If Frida wasn't her friend, Main might be dead already. Benno is a bit unreasonable for blaming Main for making deals with Frida. Besides, Frida is paying her quite handsomely. She's haggling with her far less than Benno himself. What Benno went through with Frida's grandfather is Benno's own problem. It has got nothing to do with Main, who's friends with Frida.
I think it isn't mentioned here, but in the LN he actually clarifies that the money was used to get the materials for the magic contract (which are expensive af bc of magic things and so).
Also, the Guildmaster is not so bad, but he has a problem to understand relationships outside of merchant perspective. When Benno's dad died he wanted to support them but couldn't do it without raising suspicions of favouritism, so he proposed to Benno's mom (being insensitive to her grief, yes, and that is a problem) because many employees and clients lost faith in the company and left, Mark is pretty much Benno's right hand cuz he stayed even in those harsh times. They got dangerously close to red numbers (or got in them, idr) and the guildmaster could not help directly from his position, and was insensitive and forceful, which is what led to his rivalry with Benno.
Also, he helped Myne as much as he could when informed of her getting into the temple. He had to be informed by the High Priest because he was collecting info about Myne's workshop, and the guildmaster vouched in her favor as much as he could so she could keep her workshop and get treated well.
Not the best, not the worst, pretty sure still insufferable tho