Keep total balance transfer to 30% utilization of card, or max out transfer promo?

Hello all. I am working on clearing some CC debt. I'm carrying about 17.5k on a card that's recently gone up to about 21% interest.

I won't bore anyone with my long story, but briefly, I was sick for over three years after Covid and am just now able to work again in my own business. In that time my wife had to support us, as I was basically disabled to the point where my health was all I could focus on. Savings ran out, etc. I also support an elderly parent, so the debt grew in that time with medical bills and I admit that to not stress my wife out even more, I put car repairs, home repairs, and things that came up on my card. I was keeping up with paying 2x the min but the interest raising just killed me. It went from about 11% to now 21% or so. I would make big dents before and then something would pop up again and I'd go backwards again. Now I literally don't spend on the card and with my payment each month, the balance just stays where it is.

I made some changes to our budget this month, where I now have about 1k a month to tackle the amount. To save some interest, I opened a new CC that has a 0% APR on Balance Transfers for 12 months, with a 3% transfer fee. They are allowing me to transfer up to $5,500.00 of debt to the card. However, that would essentially take the utilization of this new account to over 73%. I'm not sure if that's wise.

Would it be better to just transfer over enough debt to make some interest savings valuable, say $2,500.00-$3,000, so the card utilization remains reasonable? Or is it best to just max out what they are offering to lend me?

I have some assets to sell so my plan is to move over some balance, and then what's left on the high interest card to make a series of larger payments as I sell some investments over the next few months, etc. as well as work this extra 1k towards what's left.

The card I obtained is a credit card my wife already has that I am an authorized user on. I just opened up my own for the transfer offer and hopefully done responsibly later, it will be a useful card. We've had a long history and do not carry any balance on that card. I did this because I can immediately sock drawer that card and only use it for this transfer offer and nothing else. It's already locked in my safe.

I'd be thankful for any advice?