Question

1
Many years ago I heard a rabbi speak about the prohibition against giving and receiving bribes in any public role, not only for a judge. He argued that this is a Torah prohibition. I don’t remember what his source was; can the Rabbi tell me?
2
I have been a gabbai for many years in some ordinary community, mostly people with modest to low incomes, and I am like them.
We have one person in the community who has a great deal of money, apparently truly wealthy, but he is a person with a bad nature: he kvetches, complains, remarks, criticizes, takes jabs, is bitter, and makes those around him miserable. That is simply his nature. It is impossible to hear from him anything good, nice, or complimentary about anything in the world.
He has decided that he is a professional prayer leader. He is indeed musical, but he does not know how to read well—maybe some kind of disability—and practically speaking, he mixes up letters. He reads words with terrible distortion, even in the blessings themselves, and out loud…
During the year it is somehow tolerable, because he probably hears from everyone how it is supposed to be read, but on the High Holidays it is really awful.
I suffer because of him every single year all over again.
The congregation—some are indifferent or tolerant of his mistakes and distortions, while for some it is disturbing and embarrassing (we are hundreds of male and female worshippers)—and that is reason enough not to let him be the prayer leader on the High Holidays.
But there is another reason: every year, and over many years, every role I have given him has caused me great and prolonged suffering, with many times more trouble and hassle than all the rest of the prayer and holiday organization matters combined.
He does not do what I tell him, argues about every instruction, always has something to say, always makes a fuss, and goes around explaining to everyone how stupid the gabbai is, how he doesn’t know how to calculate the times, and understands absolutely nothing. He always has customs different from what I tell him, and he pesters me before, after, and during the holidays, and I am not exaggerating at all.
Every year I again swear not to give him anything in the future, but again and again I pity him, and again and again I regret it, because every time he is a genius at inventing claims, grievances, and annoyances—how bad our community is, how good other communities are—relentless nagging from underground, just negativity all day every day.
Bottom line: last year I stood firm and gave him nothing. True, I suffered harassment over the fact that I did not give such a great prayer leader as him a role, and instead gave it to lesser people… but as I expected, the harassment over not giving him a role is half or a quarter of what it is when I do give him a role, because then he feels important, gets arrogant, and gets busy harassing people.
 
This year I am fully resolved not to give him anything, and to suffer a little because of that rather than a lot when he has a role.
He understood which way the wind was blowing and offered me a large sum if he gets a role.
So now the question is:
Am I allowed to accept the bribe and give him a role? After all, the main reason I am not giving it to him is because I suffer, not because the congregation suffers because of his disability. For the sake of the funding, am I allowed to tolerate his harassment and give him a role? And would the law be different if he donates the treasure to the synagogue?