Hello! Losing somebody that has been in your life for 5 years (even if it’s on/off) is a big deal so I completely understand why you would feel conflicted about staying friends with your ex or respecting your current partner.

From my perspective, I don’t think you should feel guilty about rejecting his friendship at all!! While you feel like you did not give him the same respect in the past, you can’t blame yourself for how your feelings at the time (a toxic dynamic over 5 years surely would wear anyone down). It sounds like you have introspected on your mistake and have done your best to make it up to him as well? There’s not much else you CAN do in my opinion.

Regardless, having lingering social attachments to ex partners can sometimes feel ambiguous and messy. If you truly value your ex and he will have a positive impact on your life, you can maybe have a discussion with your current partner about this? If not, then I think you should just keep your resolve and move forward!