Default Judgment for CC debt

I'm in Ohio for reference.... So I was sued by Javitch block back in 2011 for an unpaid cc debt. I was never "served" and did not know about it until years later. The information on the public record shows they mailed it to a prior address several times and apparently were able to get a default judgement after no response. Skip to today. I have no negative information pertaining to this on my credit reports. I just received a letter from Javitch block stating they will accept half of the original debt. Should I pay?

Reasons that I may not want to pay/ Concerns:
1. Do I have a foot to stand on since I never received the summons?
2. I am worried that when I pay, it will than show up on my credit report and remain there for 7 years.
3. I have read a judgement can become dormant after 5 years. How do I know if it is dormant (where it can no longer be enforced and does not accumulate interest)? Do they have to take steps to revive it that I would be notified of and could I decide to settle if/when that happens?
4. Can I further negotiate with them? If I am legally bound to pay them why would they be offering to accept half? The judgement allows for non-wage garnishment so I believe they would be able to just take the full amount out of my bank.

Thanks for taking the time to read and if you have any information/advice that you believe would be beneficial to me, I would appreciate a response.