I've identified some OSINT Sources but they are not enough. Can anyone identify other sources to automatically via APIs or other way to collect threat intel information.
The best one I've come across for non-Darkweb OSINT gathering so far is the tool named "Harpoon" written in python3. As you pointed out, there are multiple ways to gather OSINT data but aggregating them is a herculean task for the analysts. Harpoon makes it easier with API integrations to grab different types of OSINT information and it's pretty easy to setup.
Follow the link https://www.randhome.io/blog/2018/02/23/harpoon-an-osint-/-threat-intelligence-tool/ for more information on how to Install and use Harpoon!
With regards to Darkweb, I found this tool really helpful but it's still kind of work in progress and is again written in python3. This tool makes use of Tor and is one of the requirements for it's onion crawler to function. More at https://github.com/DedSecInside/TorBot
Hope it helps!