Don't respond to everything. He is could just be testing to see if he can get you back where he wants you. If it is really a necessary communication respond. If it is not, you decide.
And remember that you are GALing, so delays should be something he gets used to. Also, I'm not telling you to lie, but if you are out doing something GAL, a little "Sorry I was out w/ friends and didn't see this." Or "Had plans & was running a bit late so I couldn't look at this until now." Doesn't have to be plans with friends, but if you have plans for something, you had plans. Also, sometimes apologize for the delay, but other times, just matter of fact. You don't want to have him thinking you feel obliged to get right back to him, it is just something polite you say every now and then when you are in the mood.
If it is just him expressing well wishes or love, those don't require a response at all. He is just expressing himself. Of course he is fishing for a response in kind, but let him keep fishing esp. mostly. An occasional thanks or 'thanks, I'm doing well' or 'thanks I'll do that' depending on the message content is fine. But he has left & filed, and it is time to realize better what that life is going to be like.
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15