My product happens to be project management software, my differentiator would be providing all the key features for dev teams while keeping the software very simple.
As part of pitching to my local enterprise board for the money, I have to get across a clear vision of how I get from MVP to a successful company.
A bad way of doing that is saying I will get 200 new subscriptions per month, another bad way is saying competitor x made $800k in their first 2 years and I think I can match it. What is a good way of getting this across when you do not have data such as adwords conversion rates, cold calling success rates and things like this which would back up your claims and what are the most successful way's to grow a company quickly that are achievable and not pie in the sky type of stuff.
You answered your own question yourself. You need some kind of, "data such as adwords conversion rates, cold calling success rates and things like this which would back up your claims"
Without any kind of data which you've collected on your MVP, you can't make any statements on growth potential that any investors will actually believe.
Without data you're just pitching an idea. While good ideas are needed, the investors need to see that _you_ are the right person to make and sell your idea successfully. You need your own personal data on your own MVP to prove that. You can't just say, "these smart guys from company Y were able to do X growth, so that means I'll get X growth too".
I think you should wait on attempting to get funding for anything beyond MVP. Whatever numbers you come up with for your current plan are going to be pure speculation.
What I would do is create a funding plan for just the MVP. Get the MVP built and get a bit of traction then go for the next round.
You need to know the size of the market, the market share taken by existing competitors. You need to make a case for why your differentiating factor is really a differentiating factor.
Are there user reviews of people talking about the lack of key features for dev teams and lack of simplicity in existing software products?
If you know your market you can actually pre-market your MVP idea. Using Adwords, FB, LinkedIn ads and a landing page you can attempt to pre-sell what your MVP is going to be to gauge interest and market sentiment.