Most people look at what their blood sugar is before fasting (and with no short acting insulin on board) and see whether it changes over the fasting period. The obvious time to check is overnight, is your morning level roughly the same as your night time level? Given you don't want to inject or eat at night, I'd assume that if my night time levels are right then my basal is OK.
People's basal needs can vary by time of day and hence some people split their basal dose to cope with varying needs, and others move to a pump.
And though if your weight goes up your basal needs will probably go up too, the amount varies so much from person to person that the divide your weight by 4 rule is even less use than the (1 unit of insulin per 10g of carbs) that some people start their bolus ratios at.
Do you have a correction ratio as well as a ratio of insulin to carbs for your bolus?
Good luck