Reaching out first when he replies slowly: is it weird?

Start by sorting his slowness into two kinds. The first is someone who answers everything, just late, usually at the end of his day. The second is someone who answers fast when he's into a conversation and goes quiet when he isn't. Your message history will show which one you're dealing with. If his replies to you always come after the same delay regardless of what you sent, that's habit, and a text from you is not a referendum on how he feels. If the gap grows when the conversation gets personal or when you suggest meeting, that's a more useful signal. Also check what he does when he initiates. A guy who texts first at night and then vanishes for a day is treating the phone as his own space, not as a place to talk to you. Look back at the last five delays before you decide anything, because memory tends to hold onto the one long gap and forget the three quick ones.

The useful moves here are about shape, not wording. Give him one thing to respond to, not a stack of questions that each need a decision. Pick something with a natural short answer, like a yes or a choice between two options, because slow repliers tend to send short answers. Refer to something from the actual thread so he can see you were paying attention, which also tells him you aren't starting from scratch each time. Keep the message lighter than it feels to you. If you're anxious about the delay, it will show in length and in how many question marks you use, and both make the message feel heavy. Leave the next topic open so he can pick it up himself. The message should also make sense on its own, so if he answers it three days later, nothing depends on a text you sent before it.

Wait based on his reply cycle, not on your own patience clock. If he usually answers within a day, give it about two days before you follow up. If he's a three day replier, a follow up after one day looks like pressure. One follow up is reasonable, and it should be a new small thing rather than a question about whether he saw your first message, because a checking message asks him to justify the silence. If that gets nothing back, or a short reply that doesn't open anything, stop initiating for a while. Give it about a week and see whether he starts something himself. If he doesn't, you have your answer about how much room he's giving this. Staying the only one who ever texts is how people end up stuck in threads that go nowhere, so the quiet stretch is information, not a punishment for him.