Right now the title is the same as the text in the email itself (very long and looks like spam)
Please try putting a single line of text into the text element. The first line should be split from the rest and be used as subject.
I've tried to use HTML code but it just shows up as plain text in the email.
Yes, the email is currently intended to be sent as plain text. The request to use HTML mails has not been articulated so far.
There is also a second paragraph of text in the email stating the email address associated with my SoSci account which is not customizable at all.
This is intended in order to guarantee that respondents have a valid contact option. Unfortunately, some users would not like to provide a contact option, and then all the requests go to SoSci Survey (who, of course, cannot give the respondents usefule answers).
is a risk it will reach malicious people who will send spam to the email
Of course, you can create a second account on www.soscisurvey.de with the project's email address and make this account the primary mailing account (in the SoSci project settings).
Actually, there are very few questions about the pause-feature, therefore, the manual is quite short. But regarding the primary mail address, please see Shared Access to Projects and Send Email to a Personal Contact