Fix each issue separately. Disconnect the kickdown linkage from carb. Reattach throttle return spring and see what the idle issue is. 1500 is way too much unless you modified your motor above stock spec.

Once you have idle fixed, then reattach kickdown linkage and adjust it. You should send a photo with top view of of your linkages. I think its just adjustment for trans. You do know there is adjustment for the kickdown as seen on video. You do need to see if you are getting WOT and you said you haven't checked. Need to report that you did check.

Without being there, hard to tell what your issue is. I mentioned if your fast idle cam is interfering with your warm idle performance. Fast idle cam is used when cold and choke closed. If that stuff is not sorted, then that will contribute to fast idle that you cannot get down.