Without knowing what your partner does for a job it's difficult to consider why a female colleague would call at such a time. Although, your partner had admitted that he has called out the co-worker and rightly so and has taken steps to prevent further incident. Has this worked? Is the co-worker contacting your partner less? The screenshots are odd, but not unexplainable.
For whatever reason, you've connected with an old college friend and you have been open with this to your partner however, it's not been mentioned how close you were to your college friend. If your partner isn't aware of the type of friendship you had, this may cause concern.
Men are quite cave-man-like in that if they feel threatenned or worried their partner could be swooped away by another man, they may look to 'Peacock' to show that their partner should remain with them.
My expirience? 10 years of marriage 16 years together and two children.
You've been married 10 years, arguably, in that time you know your partner better than anyone else. I wouldn't jump too quickly to conclusions or even asking online for others' views as this could cause you to go into overdrive and consider 'worst case scenarios'. Also, 10 years is a long time, people become too relaxed and forget to make time for one another and suddenly a lught bulb moment happens and you realise you've been room mates for a little while instead of life partners.
Sit down with your partner, have a drink of your chosing each (tea is usually preferable) and have a discussion. Don't allow for emotions to become involved as things may escalate and you risk damaging your relationship or both parties becoming angry and it turns into 'tit for tat'. Simply ask your partner why they have been treating you so much - 'Why have you been treating me to so many nice things latley?'.
You could also ask why there are screenshots on his IPad of another girl but you would have to give reasons as to why you looked in the first place. Again don't let emotions take over and instead of accusing replace what you want to say with 'I feel/felt'.
Bare in mind, your partner may also ask you questions around your friend as he may have the same concerns as you but from the other perspective.
It's not controlling behaviour on your partners behalf unless he is controlling what you wear, where you can go, who you can talk to, your finances, access to your own devices etc. If he is doing these things then you should reach out to a friend for support and contact your local domestic violence support networks avaliable to you that can be found on your local Police website.
In summary, ask your partner, they are the only person who can answer the questions you have and reassure or confirm anything to you. Online can be a place that is quick to feed you more concerns and worry.