AddOpenIdConnect with external IDP in .net core web api with angular client app

Question

I am developing an angular +.net core web app(not to be confused with .net core MVC web app). My UI client uses angular, my backend web api's use .net core 6. I am using external IDP to authenticate my angular app for that I am using AddOpenIdConnect. All though I am not using MVC for my other APIs(using web api type controller) but I pulled in couple of MVC controller(Home and Account) from the sample app present in external IDP's sample project(as I could not find a way how to achieve it with my APIs).

On login button press in my angular app I call this method of Account controller which redirects me to external IDP. After successful authentication I am being redirected to my angular app's landing page (http://localhost:4200/admin) which solves my purpose as far as SSO is concerned. Also in OnTokenValidated event I am getting the access token as well.

Now the problem I have with this approach is:

1. How can I return this token to my angular app(which is an independent SPA) so that it can be used as authguard for the angular app and for safe guarding other api end points? I am thinking of making another end point which angular app would call after successful redirection which would return the claims and access token to UI. I tried fetching it from HTTPContext in the end point that I made but it is coming out to be null and User.IsAuthenticated as false.

2. How can I secure my web api end points with this same access token? I am thinking of using the access token returned to UI after redirection for authentication and then it can be sent back to backend apis in header for authentication. How can I achieve that?

3. All the example and sample code(even on IDP's website) use .net core MVC. Did I make a mistake by making it a web api project?