No need for a day light at all. It's a snake so you don't need a UVB bulb. Also you have the heat mat so you don't need a heat bulb. That's what the mats for and they are better to use then bulbs as wellas they don't dry out the tank and you can maintain the heat better. Also make sure you have something on the mat to regulate the heat. A thermostat or rheostat/dimmer. Without these the heat mat WILL get too hot.
If you want the lamp just to ad some light to the tank then use the lowest wattage possible with a fluorescent bulb.
Yes when you change cage give him a week with no handling to adjust. It's no different then binging a new animal home. A 40g can sometimes be recommended as the right size for an adult carpet python on care sheets but they are actually a little bit small. If you just moved him from a 10g he is obviously still growing so the 40 works but a 4X2 foot tank is what you should use once the snake is full grown.