Water conditioner is not optional.
In a tank/bowl of this size I would do daily water changes - alternating 50% and 100% every other day. He should be scooped in a little plastic solo type cup and not use a net. New water should be the exact same temp as old water - matched using his in tank thermometer. Water and conditioner should also be premixed (you can use fresh water jugs from the grocery store - rinsed well in hot water but not chems).
However, bettas cannot be kept healthy for too long in a container of this size. 2 gallons is minimum.
He is also freezing at room temp, and any swings (like if you let your house drop at night) are hard on him. They can even be lethal. You need a heater that can keep a constant unchanging temp between 78-80F. In a 2G you can get a 25w adjustable heater. Make sure any heater you get is tested 24hours in similar size container to make sure it will maintain a constant appropriate temp. You must always use an in tank thermometer to monitor the temp. He must be acclimated to the water water either by floating in a cup inside the already fully warmed water for a hour, or by adjusting the heater to increase no more than 1 degree per hour and 5 degrees per day.
He should be getting two small meals a day, at least a couple at a time and one fast day a week. However, your pellet is low quality which can lead to constipation issues. You should look for a pellet whose first two or three ingredients are whole fish and not fish meal or wheat.