Well, first of all you need to know what you want. Apart that you just said that you dont want any fancy pants maps and charts - I totally get you on that because it is that you wouldnt probably present in that fancy way to anybody but you ooooor maybe your friends but deffo not to potential employer. You also said that you dont want any subscription. So my guess on that is to use good old fashioned excel file. I'm using one myself and even tho that I'm not flying professionally yet then I've set some foundations on calculating night/day time. There are many tools to do so based on given gps coords and date also available in excel.
In general you can get basically anything you need in excel - you just need to find someone who is good enough to program it for you. It wont be cheap probably based on amount of stuff you want to have there. But most likely it will be one time payment. Then you can store it on some kind of cloud storage to have it secured + available and synced from any device you need.