From your description it sounds like you are using a Task List rather than a standard List. If you are using SP 2013 you can check this by looking at Site Contents - if the icon for your list is a 'clipboard with a tick mark' you have a Task List; if it is an icon with 'four columns and a header' you have a standard List. (The list url does not distinguish between the list types it seems).
If you are using the Task List, to change the behaviour of the calendar go in List Settings/go to Views/select the name of the calendar-style view to edit it. Look for the Time Inverval header. Here you can select two dates fields, a 'start date' and an 'end date'. You can change the settings here.
Since your calendar does not display anything at present (due to the lack of an end date) perhaps you could create a field anticipated end date? - this would make the calendar display your items. Failing that you can select your two dates using the same field (e.g. start date), then SP will display your item.
One other thing. SP calendars can become cluttered when there are lots of items, so you might need more than one view to display items cleanly (e.g. severity / category / site affected).