My Boyfriend [36M] recently decided to quit his job to take a break for a few months and now wants to change how we split finances

Background info: We have been dating for 3 years, living together for 2. I [28] am 7 years younger than him, which is relevant later because I have fewer years spent progressing my career / earning potential and building savings.
When we moved in together, he made ~140k and I made ~90k. We eventually got raises and he made 180k and I made 110k. We live in San Francisco and it is expensive. I had gone through an expensive career change and moved here with a much lower salary than I had before and I work for a startup. He did the same thing 8 years ago (when he was my age now) and back then was making ~70k, and he talks about how much budgeting he had to do to survive. Now that we have been dating for a while he often forgets completely that I am 7 years behind him in my career and I'll need to remind him now and then.
For our entire relationship he has been very very pro 50/50 for everything - chores, expenses, etc. This is just his personality in general about everything - everything should be fair and equal. I am generally more "today you, tomorrow me", I don't need to feel that chores are split evenly, etc. In fact I think it is healthy in a relationship to want to go above and beyond for your partner just because, do surprise favors, etc - without keeping track and expecting anything in return (as long as it is generally give and take, and not all give). On paper he agrees with this too.
So when we moved in together (which he originally pushed for as it was a bit earlier than I wanted) he wanted to split rent and expenses 50/50, and I just could not afford that without living with roommates. I told him what I could afford, and we talked about the standard of living he and I both wanted, and we compromised on splitting rent based on proportion of income, and splitting all utilities and bills 50/50. Our rent is $3400.
This comes out to me paying 43% of monthly expenses, and him paying 56%, as our monthly expenses are about 3/4 of what rent is.
Now even before he quit his job, this was a small source of resentment for both of us.

• He still feels as though he is "supplementing my lifestyle and I get the luxury of living in an apartment above my means at his expense" without a full 50/50 split
• I still feel that we are not fair in terms of savings, as he is pocketing more a lot in savings every month while I feel I am struggling to try to save money.
• I feel a good portion of our monthly expenses come from him, and everything we plan seems to go through a "lifestyle creep" (for example every month he spends 4x more than I do on groceries for the house. Another example is I had planned us a vacation that was a fairly cheap road trip across California, and somehow it got substituted for a very expensive trip to Hawaii because he had never been). I do take full individual responsibility for this as I find it hard to say no, and often don't even realize it is happening.
• If we break up, he walks away having kept growing his savings during our relationship, while I severely reduced the amount I was able to save during the course of our relationship. This is why I was against a full 50/50 split - if we had done this I would have been saving $0 per month.

Now, 3 months ago he decided he was tired of working at the company he had been working at for 8 years (he helped build the company and was in an executive position and burnt out), he had savings to last him comfortably for ~9-12 months of expenses (and he has more savings he is keeping to buy a house etc), and he needed a break for his happiness. He quit his job and has been funemployed since - he is relaxing, playing video games, working out, and thinking about what he wants to do next. He stills works a few hours every week contracting for his old company.
Recently he has discussed the option of him traveling a bit during this time as he continues to find what makes him happy (although this was 3 weeks ago before coronavirus craziness), and now he wants to finally split rent 50/50 because he does not have his full time income anymore, and he does not think the arrangement is fair anymore.
I am having a hard time explaining to him why this is frustrating to me. Some of my points are:

• We moved in with an agreed method of splitting rent. I was prepared to pay more rent / even pay more than him as I increased my salary (I have been interviewing, and actually got a job offer for $150k in another city but turned it down because it wouldn't work for us)
• This would be an entirely different conversation if he had been laid off or left involuntary - but he quit of his own free will knowing full well the consequences. I feel as though now my financial burden is increasing entirely through his choice, and he has no intent on finding a new job any time soon while he continues to live off his savings.
• Again, this would be an entirely different conversation is we were engaged / married, as in that case I would not see it as "my/your money" - but again, if we break up, I don't wan't to foolishly put myself into debt or financial hardship without the declaration of intent that this is a partnership we are both committed 100% to in this form.

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While I understand his point, he doesn't agree with any of my points, and I am having a hard time explaining to him what I feel. He keeps using the term "funding my lifestyle that is above my means" this is really annoying me because it does not feel like a partnership, and honestly this is the downside you get for dating someone 7 years younger than you who is still trying hard to "make it" - I just don't make as much money as him! It feels like he does not see anything from my perspective at all. I would love to hear any advice on how to communicate my points and if anyone has any advice from similar situations. Thanks!
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[TL/DR] Boyfriend quit his job as an executive making a high salary because he wanted to relax for many months and take a break. Now wants me to pay more than what we had agreed before on monthly expenses


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