Hi Grigoris,
For your 1st option, it looks like you should be able to create a
custom remarketing tag for this. For more information about that, I would recommend reaching out to the Google Ads Product Team
here as they will be more equipped to assist you.
For your second option, if you are able to get the list of users (email address or address) from the segment, you can upload them as a
Customer Match user list.
One other option I can think of is creating two separate user lists, a
Basic user list for cart abandoners (defined as a conversion action) and a Rule-based user list for members over 65. Then, as explained
here, create a
Multiple user list where you AND those 2 lists together.