There are no informal greetings, nor endings. The beginning of the message and, respectively, the end, both contain only the names of the recipient, respectively, the sender.
The following personal pronouns have been omitted: I (from: going to martial arts class), I (from: Will be home late), you (from: so please make salad), I (from: Should be home by 8:30)
The following articles have been omitted: at (from: Class ends 8pm), a (from: please make salad) and the (from: Vegetables in fridge)
The auxiliary am (to be) has been omitted from going to martial arts class. The auxiliary are has also been omitted from Vegetables in fridge.
The only imperative is Thanks!
The participle in the given text is forgot.
I couldn't find any informal linkers.
The abbreviations in the message are: Thanks (from: Thank you) and Tues (from: Tuesday)