Good evening and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the weird login requests you are receiving.
I would love to help you with this topic.
As a first troubleshooting step, could you please provide us with your complete system information in a private reply using the instructions found in the following link?
https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Secondly, by the looks of it, I believe you would benefit from using a plugin such as Theme my login: https://wordpress.org/plugins/theme-my-login/
This will let you keep the login on the front-end as well as add a captcha (among many things).
Let me know if that helps.
Have a great day!
Geoff B.