Help Nesting a Formula

[jnix612]

I have attached the spreadsheet with the same information below:

The formula (dates)
Days Open = Ticket Completed - Ticket Opened - Days On-Hold
=IF(J6="","",IF(ISBLANK(L6), TODAY()-J6,L6-J6-M6))

Works as seen, however if Ticket Opened is blank, the formula does not cover that option and the formula does not calculate.

Next Teachable Moment:
Can you show me how I would nest a format into the above formula? Instead of showing 109 days, show 1 month 2 days.
Note, I'm not going to use this format on the table. Instead, I will show this format on the dashboard (I am comfortable with converting). I simply want to learn how this is nested into the above formula.

Thank you in advance.