Thank you for reaching out to the Community about your email. I apologize for any inconvenience caused from you not being able to tab your text! You are correct, at this time our email editor does not have the ability to insert tabs. This is however a feature request submitted to our Product Team on your behalf. As a workaround you do have the option of copying text that includes a tab from an outside source. Our editor will recognize it as non-breaking spaces and they remain after saving. You can also add underscores and change the font color to match the background color.
As for your space bar deleting text, this is not an experience I was able to replicate. Is this happening for you in more than one browser? Does the space bar continue to delete text after hitting the insert button on your keyboard? We have seen cases where users unknowingly hit their insert button. This insert key will cause you to overwrite text to the right of the cursor as you type.