well, i am doing same exact thing.
autocrawler and download video from source and directly upload it to cdn (openload)
as of uploading to WordPress it could be done using wp-api.
for me, i am not using WordPress, instead i am writing script that pull the list of videos directly from openload and display the embed video on the web.
as of watermark and automatically upload to tube, it is possible, but need a lot of programming knowledge to achieve that.
but, i honestly think that uploading it manually to tube is still good enough since the point of that is to gain attention and exposure to our website through watermark, one or two video per day is already enough and not that painful to do it manually.