I do not think that two times having sex makes vagina too loose but at the same time it is impossible to tell that the vagina is loose just because she had sex twice. There are many factors makes vagina loose like some women have natural loose vagina and she might be one of them so do not doubt that she had sex with her boyfriend more than two times.
I would say since you do not have any evidence about her past just believe her words and be happy with her. Moreover, you should not judge your wife based on her past and it is a really good thing that she told you about her past herself so respect her past and be happy with her as that is what you have.
As far as your second doubt is concerned, there are strong suspicious that she had sex with her boyfriend in your absence but again you do not have any solid proof so it would be foolish to hold her accuse without any evidence so the benefit of the doubt goes to her but I would say one thing that you should keep your third eye open and try to find out the more evidences to conform that she cheated on you where you are out of the town for the interview with her boyfriend.
One thing you should ask her why she did call her boyfriend in your absence and see her responses because her responses would tell you the most the story about her activities but only accuse her of cheating when you found out solid reason as it is a really sensitive issue.