peer review - Conflict with conference Program Committee

I was reviewing a paper for a conference. As I wrote in the review, it was IMO a completely average paper (boring problem, boring techniques, average write-up). I gave a scoring of "0" (ranging from -3 to +3) noting that it could, potentially, deserve publication if there is any space.

After submitting my review, I received a message from the program chair saying roughly the following:

as you can check there are some rather different reviews regarding this submission. Please feel free to comment on it or change your score in case you think it is appropriate.

There were 2 other reviews: The 1st liked the paper and gave a +2. The 2nd however had virtually the same review as mine but felt probably slightly more generous and gave a score of +1.

1st minor Question: Is it normal PC members to ask you change the review score when the review does not vary significantly from the others? I never heard such a thing, even in personal cases where was a large deviation between reviewers.

I was trying to understand the logic behind the PC message. My Theory:

I think the PC members wanted to accept the paper but because they did not have an overwhelming argument and because the average review score was lower than the acceptance threshold they were unable to justify the acceptance. Instead of altering my score at their own will, they asked me gently if I am willing to do that.

Is my theory plausible?

2nd minor Question: Since my review was virtually the same to the one of the 3rd reviewer, wouldn't it be more fair if all other parties were involved in that exchange? Maybe the 3rd reviewer would have change the score to "0" after reading my response. Why this process should involve only me?

I responded by noting the above and by standing by my initial decision and score because I really felt it did not deserve anything more than "0".

3rd Minor Question: Do you think my response was appropriate, given the circumstances? Was there any other way that I could have handled the issue?

Now, this is my final (conditional) main question:

Given the fact that my "theory" is correct and given the particular circumstances (slight variation on reviewer opinion), is it common to ask the reviewer to do their (the PC's) job of accepting/rejecting manuscripts when the reviewer's job is to provide an honest opinion? If yes, shouldn't all reviewers be aware (in case there is not some terrible misunderstanding/mistake in any of the reviews, just a matter of opinion).

Note: I was told after the event, that I was the only one that received that message. My guess is that the paper was close to acceptance but my score prevented it from being a clear accept (so they felt I was somewhat "harsh"). I guess that also explains why they did not contacted the +1 reviewer B (also to avoid situations that I change to +1 and B change to 0 after reading my justification, and we are at square 1). Any thoughts on that? Is this common?