TL:DR put separation at the bottom of your list and try everything else first.
You want an opinion. I can give you a grab bag of little thoughts. I can broadly only speak from my experience - being in a long relationship I've become more interested in how and why it seems to work for me - I often astounded by the complexity and apparent contradictions I see in it - I count myself lucky and I'm happy but we're all different as individuals, have wildly differing views on what relationships should be and I think the internal mechanics between couples can also be very different - there's obviously a lot of important info missing from your post so it's easy for someone else's thoughts to be right off base.
So - I'm a believer in the power and benefits of being in a relationships - well - one that works - I think you (can) make better progress in life as a couple - better for your mental health - sense of well being, personal sense of security, financial resilience - against all the unpredictable things that come everyone's way once in a while. So my view is I see "the relationship" as an entity in itself that is worth investing in.
IMHO relationships generally always involve effort - you have to work at it. Obviously there are times when everything flows so beautifully and effortlessly but I always think these times come from the effort you've been putting in beforehand. If you want something out of a relationship - you have to put something in - and IME this is something that has to go on almost every minute of every day. My relationship would never work if I spent 100% or even anywhere near 50% of the day thinking about what I want out of life or the relationship - the more time I spend thinking about her or "our relationship" - the better; you can't be a rock embedded in the sand on a beach waiting for the tide to sweep in and caress you twice a day - be the wave not the rock.
When you say "going through the motions" - is it that you have both run out of steam and aren't really making much effort for each other or making plans? If you're saying he's an amicable partner and the relationship has been "OK" (-ish) it's not a bad starting point - do you not just need to inject some life into rekindling it? I think it is easy to settle into routines - it's laziness really IMHO. I think learning to embrace uncertainty is one of the best things you can do for yourself (and teach your kids if you have any) - there's a lot of things that happen that might have a big impact on your life - someone falls ill, short-term, chronic or terminal, someone dies, someone has an accident, loses a job, loses a close family member, etc - in going through all of these things, dealing with them processing them - I find you grow and discover things that you might never have discovered any other way - so I think that learning to embrace the uncertainty of life and change is a positive thing - or can be - so I'm inclined to invite it in - so what I'm saying, my outlook - is that perhaps you need to shake things up a bit and do something different - maybe you and your partner can talk and find something different that you'd like to do with your life together - you really do have to "dream your way forward" in life. Does he agree that your relationship is in the doldrums ATM? Does he understand that's how you feel?
As always - communication is so important - how well have you delved into each other? Were these deep conversations something you only had at the start of your relationship or didn't you get into them even then? I think you need these all the time because you both change in different ways. Communication means getting to know how your partner things and feels and also about letting them know the same about you - you've really got to understand each other and to do that you've got to be really (really!) honest - this life is for real - it's not a rehearsal. Me and my wife are very different in many ways and have different aspirations but one key thing is that we both want and like being in the relationship - so I think we both work at it. We don't catastrophise about the relationship when things aren't going well - deep down nothing worries me - we have problems but we find a way to either sort them out, or reframe them and live with them, or agree to disagree - generally nothing is worth blowing the relationship up for (OK infidelity is probably the deal breaker). IME it takes a lot less to get the relationship back on track than some people might think - I think thinking about yourself too much is the main problem in a lot of relationships.
Is the relationship really "a" or "the" problem or are there other things going on - are you depressed? Is he stressed?
Apologies if I'm wrong about this but you seem very vague about what the problem is and what you want - if that's the case why would you think you'd be any happier on your own? You mention wanting time on your own and independence - can you flesh that out a bit - time for what? Have you not talked about what you want in terms of free time to do with as you please? Or is it freedom to make decisions about things - is it always hard to get him to agree to anything you want? What is it that you want to do that he doesn't? Is this about everyday domestic things like house or garden or what to do in life? Relationships do change - you change, your partner changes, what you want out of life and love changes - people are allowed to change - you have to keep talking about these things to stay on the same page - so IME there's always a changing dynamic - a tension - that you have to learn to deal with - I'd hate to be back in my relationship of 5, 10, 15...30 years ago - I wouldn't want either of us to be those people.
Hopefully - you'll get some other opinions and ideas here - MN sometimes resembles a river infested with crocodiles waiting for Bambi to appear at the water's edge.... it's not always that bad though!