I'll start by agreeing with what Dan said re: how timing of raising the funds impacts your ownership of the project, and that later (or never) is the best time to raise funds from that aspect. However, it isn't quite that simple, as I'm sure you know.

I would want you to consider 2 simple things (I'm not armed with enough information to analyze it myself - but feel free to private message me with details):

1. Expert validation is great - but how many actual users have interacted with your prototype? If the answer is none - or less than 100 - don't raise funds, get more users on the prototype.

2. Development of the app never stops (software right?) - but sometimes it needs to pause while people use it (so you can observe their use in detail) - or you are needlessly polishing.

Make sure that the "improvements" you make are steeped in findings from actual users, and that it actually improves their experience / outcomes in using your app. Too often, I see brilliant inventors, creators, developers or designers remain on their lab bench tinkering away on something that desperately needs the attention of an actual user.

Anytime you think "one more feature, one more tweak" really question the need for that change, particularly in the case that it is keeping you from releasing your app (or pushing an update live).

I'd be happy to help you determine which side of this curve you currently occupy. Often, all it takes is an objective, removed perspective to provide clarity.

Cheers,

Ryan