1. How does one go about scrapping ships(or is 'Destroy Ship' and 'Delete Ship' the only option)?
Move the ship you want to scrap to a colony with a shipyard.
Open up the shipyard tab of the colony screen for that colony.
Under the "task type" dropdown select "scrap".
Select the class of the ship you want to scrap from the list and the specific ship from the second list, then hit "add task" button.
2. Is it possible to load a partial load into a cargo hold? Meaning, I currently have freighters with 15k tons capacity. Can I load 2 Infrastructure and then also minerals and/or a refinery etc. at the same time? If so, how -- it always loads up to the max when given a single order to 'Load Infrastructure' or whatever.
Under the box where you choose what order to give you should see a box marked "max amount to load" that you can use to specify how many of an item to load, as long as there is space for it.