Unfortunately, I may have more bad news (but I would rather you know it now then be surprised later).
Filing an extension does NOT give you more time to pay your tax balance due. If you do not pay by April 15, 2019, any balance still due will be subject to interest (it will keep you from getting a late filing penalty).
You can file for an installment plan to make payments for any balance due (but again, any balance not paid by 4/15 is still subject to interest).
What if I can't pay my taxes?: https://ttlc.intuit.com/replies/3301261