My question involves defamation in the state of: Arizona

I am considering making a website that reviews specific local 501(3)(c) charities, one of which I worked for previously.

I believe I understand the whole fact vs lie aspect of libel; with the exception of conversations.

I was either involved in, or witnessed conversations between members of the board and management where they openly discussed theft, dismissed reasonable employee safety concerns, and planned to mislead the public to raise funds.
1) If I have no actual proof (recordings, notes or statements) besides my witnessing or participating in the discussions - can i write about it as something i witnessed?. Or do I risk libel?

1a) If someone else posted on a local newspaper's comment section about something that they had had 'allegedly' stolen by the charity (and later returned under direction of local law enforcement), could that posting be used as evidence of prior wrongdoing? Or is it considered hearsay?

2) If someone else who worked there as well, has sent me emails with things they've witnessed - would those be considered 'facts' or opinion?

2a) For something like that, would I be better off having a comment section where others could post their 'opinions' or experiences?

2b) If someone who still works at that place or other prior workers want their information shared, can they do so anonymously within the reviews, or would it would the better option be again to use a comment section?

At one point, employee safety and purchasing radios was discussed. Initially, the chair of the board said she never feared for her safety in the administrative section of the facility (not the actual hands-on arguably dangerous section) so she didn't understand the employee concerns. After pushing the issue the Board agreed to buy the radios. A month later, I was told by the Chair, that she had been pricing them. Seven months now and despite continued requests from staff, there are no radios.
3) Would it be libel to say that "the Board is not concerned with employee safety?" (I do have emails asking for the radios, and just walking into the place you can see that there are no radios).
3a) Or would it be better to just point out in the review "that unlike some other facilities, this certain facility does not have radios." (and ignore the whole it's been brought up and ignored aspect)

The purpose behind wanting to review these [specific] charities is that they ask for funding for a noble pursuit and then (at least in the instances I've witnessed) use it to hide questionable and criminal actions; whereas other similar charities could use donations and support to a better degree. I truly wish and desire my former employer to do well; but the negligence and criminal behaviors were not stopped even when I brought it to their attention. My hope would be that donors and volunteers could pressure the board into doing the right thing when I couldn't.

And there is a slew of former employees that are looking for a place to voice their concerns and issue about negligence and abuse and such at this facility and I would highly suspect at other similar facilities. I have done some research before coming to this site, and I believe (perhaps wrongly) that if I made a forum where others could start threads to openly discuss these places that I would not be liable for comments that others made within these forums (even if it linked to my 'review site')

Thank you for your time in answering these questions.