Hi,
Thanks for using our plugins. I can see if I can help out there.
To change events wording have you tried changing the word in Swedish and not in English? Otherwise if it is not working you could use POEdit to change the Swedish Translation file.
In Week View those numbers are not part of the translation system of the plugin so as you found out that coding will not translate them.
We have a filter:
tribe_events_week_get_the_day_display
That could enable you to write some code to remove the st or th from the numbers.
Let me know if you have any follow up questions.
Thanks