@sadiq22,
Compromise.
If people waited until they were completely financially stable before they did everything, they wouldn't do much. That doesn't mean that planning and being prudent are bad things - they aren't! But you may be hesitating a bit too long.
So talk about the end of 2018 with him (and with your fiancée, of course). That is about 18 months from now.
In the meantime, be very frugal and keep as much of your money as you can. That means everything from bringing lunch to work to getting an extra few months' wearing out of a pair of shoes. You don't have to dress in rags but just try to be as good as you can be about saving money.
And go into your marriage with optimism. I would also suggest, when you have that conversation with your future father-in-law, maybe ask him about what things will be like if you need help financially. Will he help out? If he will, then great. If he says he won't, then I would say, stick to the timetable that is most comfortable for you.