Update.
I have held the line and continued "constant optimization" and he is adjusting. I've cancelled gym membership and told him that if he really wants to use the YMCA, he can get a job there -- they give a membership to employees. He complained at first but then quieted down. I also cancelled DirectTV and had not yet bought an antenna. As a result, we didn't have TV for the MLB All Star game, which chapped his backside but he didn't complain to me, he texted his dad (my ex-husband). I only know son was miffed because I got a text from ex about it ("what? No TV?").
The coupe de grace came a couple of weeks ago. We were having round 42 over whether he was allowed to spend his own money to upgrade his phone and I just flat out told him he wasn't allowed to do it because his phone was just fine and it was a waste. Put my foot down, even though it was his money. Told him he was being a consumer sukka and it was stupid. He pitched a fit about how it was "only $50."
The next morning, I rolled his butt out of bed at 7 AM and made him go to work with me all day. I park about 1.5 miles from my office and usually bike in the last bit (saves $142/ mo in parking & tolls). With him along, I decided we'd walk. So, we hiked in, taking stairs up onto a pedestrian bridge over the river. As we passed the area where the bridge and the land came together I said, out loud, "I'll have to remember this area if I'm ever homeless. It looks dry and safe." He just looked at me with deer eyes.
We spent the day in my office and took the bus to his orthodontist appointment that afternoon. On the way back, he said "bus fare is $1.50?" I replied "Yep." He said "Let's walk." So we did. We also walked back to the car that afternoon and enjoyed hearing the sound of the river under us and seeing the ospreys flying overhead. We agreed that you don't get to see that when you're in a car.
I've moved his cell service to Ting and given him an allowance of $30/ mo. I showed him all the tips/ tricks for keeping his bill low and told him that if he uses less than $30/ mo, the balance is his to keep but if he uses more, he has to cover it. It draws directly from his account so he will also have to learn to plan and reconcile his account each month.
For his birthday, I opened a Roth IRA in his name and deposited $100 in it. I'll also move over $300 that has been in his long-term savings account. It's a brokerage account and I'm teaching him how to pick solid companies to invest in. For Christmas, he'll get more money in his Roth. He found a company that looks really good and he showed me his research. I was so convinced that I bought 15 shares of his pick (I had some dividend cash sitting in my Roth, uninvested, waiting for a good opportunity).
Yesterday, I crunched the numbers in my spreadsheet and found that I have completely flipped my financial situation. In the first quarter of this year, we spent 53% of my take-home pay on living expenses and allocated about 45% to debt service and 2% to savings. April was particularly bad -- 70% of take-home spent. By September (once ETF-dust and other one-off fees have settled) we'll be spending just 39% of my take home on living costs with a whopping 58% to debt service and 2% to savings (weak emergency fund).
I called him over and showed him the difference and he seemed to get it. I showed him how I'm on track to have a significant chunk of debt paid off one year from now. I then said "I don't think our life is significantly different now, as compared to April when we spent 70% of my take home."
He didn't disagree.