Honestly, 45 minutes is one of the easier flights to handle with a young baby, so try not to stress too much, but I will say it can still feel chaotic if he decides to fuss right at boarding when everything is rushed. For takeoff and landing, latching or giving a bottle really does help with the ear pressure, so just time a feed around those moments and even if he doesn't take the full 120ml, that's fine, the sucking motion is what matters most. For formula, I'd put the tin in checked-in luggage and bring pre-measured powder in a dispenser in your carry-on with a thermos of hot water, as most airlines allow that and the cabin crew can also help with warm water on request. For the stroller, most airlines let you gate-check it, meaning you fold it at the door of the plane and collect it right at the gate when you land, which is so convenient, but do confirm with AirAsia directly since policies can change. Three days in KL with a 3-month-old is very doable, just pack more diapers and formula than you think you need, because that buffer really saves you from unnecessary anxiety when you're already in a new place.