Why is a ring that much of a difference to what you guys already have? Men and women think differently and this thread really brings this out. Women tend to take things personally when a man is madly in love with them, but puts breaks on 'legally joining assets and liabilities' (you women call it marriage but for men, we call a spade a spade). Let me explain.
I can totally relate to where your BF is coming from and going (not that I am attempting to interpret his actions or speak for him). I had something similar to yours and decided to get married after I completed my MSc, was stable in my career, and was more financially secure, so I could have some freedom just in case a baby came along early. After she gave her ultimatum (as some here are encouraging you to do) I decided to get married at the tender age of 28 yo. No fault of mine, the marriage ended soon after, and this was my high school sweet heart who I was together with for 10+ years. While there is not necessarily any parallel between the reasons for its failure and your circumstance (because I would have still been married today had she not betrayed me), you have to ACCEPT that both of you might NOT be compatible, despite the 'on the surface' reasons you gave to suggest otherwise.
The truth is men mature much later than women and the obligations and expectations of maintaining this relationship might be getting in the way of your BF pursuing his professional ambitions and coming into his own. Yes, you are at the stage where you are ready to make things official legally and settle forever, but your BF still has unresolved professional ambitions, and that is what makes you incompatible (despite the similar values, frequent sex, etc that you mention; which are just byproducts of human interaction anyway). At the core, both of you are steering down different routes. Yes he is in love and would do anything for you, but he has not come into his own person and you have to accept this, and help him to see this for himself, because he has conflicting emotions. I can also guess that privately he is stressing about all of this.
By age 30 I was divorced and have since completed a PhD and am now very much clearer what I want and what makes me happy. I remember while married there were so many expectations around having a child, buying a home, etc, which really conflicted with my inner guts. The truth is, men reach this level of maturity and stability in their mid 30s to 40s, unlike women who do in their mid 20s, not to mention the race towards childbirth and the proverbial biological clock. The fact that you guys have been together for so long as well didn't give him much room to find himself either. So my advice, if you really want to spend the rest of your life with this guy, just lay off and give him space. Call time on the relationship if you must, or reassure him that you do not want him to get married and then feel unfulfilled and then the both of you become roommates of FWBs in your young marriage. He seems to be at a very critical stage of his development and so I think you should understand and give him space to grow, WITHOUT ANY EXPECTATIONS on either side. Meaning, you both may or may not continue.
And for God's sake stop seeing it as wasting time! You have a good man it seems. The time you are spending or spent together gave you much emotional, physical/sexual, and possibly professional benefits as well. LTRs are never time wasters, they are learning curves and help us navigate different seasons in our lives. I sound like a father and I'm just 33 yo

...been through a lot and took a lot of ME time to understand life, so it follows.
All the best OP!