Set up a working method of printing, mailing and documenting your mailings
One of the best means to accomplish this plan/program is by getting yourself a very nice sized annual paper calendar. Use your calendar to note the dates you mailed to any particular addressee. Always keep your past calendars for the rest of your lives.
Certain papers you mail out will be time-sensitive. Meaning the receiver of your document is given a notice that you are telling them what they need to know, plus your notice requests their written / mailed acknowledgement within a set number of days.
Your calendar will help you keep track of the date that you expect a response. When a resonse comes, you write on your calendar that response date. Their lack of response is something you can bank on too. Your growing stack of records is precisely the ammunition you need when push comes to shove.
This whole method of administrating your household and private affairs has to be rules-driven so that your habits form in these new responsibilities. You are now taking up the responsibility to self-govern. This is a prized seat for you, one in which you will never want to relenquish.