Hello my name is Angela.
I am more than happy to assist you with your questions by giving you my honest and respectful opinion.
Unfortunately, his immaturity is creating a communication gap between the two of you, therefore, I suggest asking him to meet with you for lunch at your place (-just in case he responds in an immature manner and cancels again at the last moment at least you would not have wasted your time by going out of your home to meet him). During your lunch, have a honest and sincere conversation about your relationship and what you each want out of it and what direction you both want it to go in. Be sure to discuss the problems you shared with me and reiterate to him as often as needed in a calm voice if he begins to get angry or argumentative: you want to discuss these issues and work through them together and you do not want to fight or argue and continue your conversation.
If you both decide that you want to continue to be friends (-and maybe one day become a couple again, then I suggest first to work on the communication skills in your friendship first especially due to his immature behavior. Relationships (platonic and non-platonic) require honest and respectful communication to remain healthy and in order to grow, therefore, communication is the first place to begin since it is the basic foundation of any relationship. One way to improve the communication skills in your relationship is by doing a communication exercise. The exercise consists of both of you agreeing to read and discuss a self help book(s) pertaining to improving the communication in your relationship along with building a closer emotional bond:
this is an inexpensive option that could improve your friendship if you both agree to do the work. If you purchase a self help book, it is important to designate the necessary time to do this work on a regular basis when the two of you will not be disturbed along with keeping a journal to write down your thoughts and reactions to what you both will read and discuss. Both of you should agree on how much time you want to spend together working solely on this and agree to how often you want to work on it, for example: once a week for thirty minutes, twice a week for thirty minutes, etc. Be sure to keep the amount of time designated for this relationship building exercise at a comfortable level for both of you so that neither of you dread doing this. The above is a healthy process that takes time to do but it can be done if you both commit to it and usually the results are positive. A few books for you to consider can be found below:
Book 3 .
If he refuses to do this simple exercise, then in my opinion he is not serious about being friends or even possibly becoming a couple again because if he is serious, he would have no problem working on the problem areas of your friendship (-this is the only way that problems will get resolved: by working on them and growing from them).