No you aren’t overreacting, given the red points…and your guy doesn’t seem honest…Soon he’ll be giving you the line “you aren’t giving me space”, you’re being insecure" to make you feel bad. It all starts with a suspicious “only a friend”.
If he loved you, he would have dropped her without you having to ask.! He’s smart enough to know that that friend is nothing but trouble, and will bring nothing but trouble given her past history (which I am assuming all happened within a year, because you tell me that this relationship with your guy has been going on for just over a year. )
My personal opinion, he’;s sitting there enjoying watching you be jealous for his ego boost, and that’s the only reason he mentioned the friend to you. he gave her the landline, so you wouldnt be able to track passed calls on his cell phone. And I wouldn’t be surprised, if this has been going on longer then it appears to you.