Hi!
Thank you for your patience.
I have replicated your WordPress installation on my end using the same plugins (to an extent – without premium ones) and I couldn’t find anything causing Tweet Wheel to malfunction.
I was also able to queue up about 1500 items at once easily, however increasing the number was causing 502 bad gateway error, which I think is in the root of your blank page being served.
Basically, servers limit requests made by scripts by time. If that time is exceeded, they throw back 502 error titled “request has timed out”. That limit varies per server, so you might try increasing it to a minute or so, so Tweet Wheel has enough time to queue up your products.
Alternatively, you can purchase the pro version which allows you to limit imported items by amount and date range. That would solve the problem.
Hope this explains the issue and thanks for choosing Tweet Wheel! =)