Credit scores really only matter when you are paying your insurance premiums or looking to get some big money loans. I mean, most of us who are responsible with money will have scores in the excellent range. The folks that don't have an excellent range, have earned that score.
DTI is certainly a thing. I've heard of people on this forum needing to take a withdrawal from investments on a monthly basiss to show "income" in order to qualify for a loan.
I was told by my loan officer not to buy a car when I was shopping for my current home. I bought 2 cars and still qualified for the mortgage on my home, even without my DW and her income on the paperwork. So, everyone's situation is different. In my case I have low DTI since I had a decent income. The bankers knew I was good for the loan, and loaned it to me. I got an excellent interest rate since I had an excellent credit score for the 2 cars and the home. I've had my DTI throttle up a bit when I maxed some CCs to cover some home remodeling. My score dropped to the "good" range and the insurance companies pounced on using that as their reasoning for raising my rates. I was still approved for more CCs since my income kept rising. Now I have 100s of thousands of available credit in my credit card, and we don't even bother putting anything in DW name anymore, since her income is so low, its not worth the hassle of her being denied. WE play the CC games, banking miles and points, and sign-up bonuses.
Get the HELOC, find a banker that gives you the best interest rate if you think you will need it.We are still down 10 to 15% from market highs depending on how you were invested, so if you sell now you take that loss and lock it in, vs if you get a HELOC with a lower rate than how much your investments declined, you are temporarily locking in the rate, and can always refinance to a lower rate (Unless rates go higher). But if rates go up, and the market goes down... well, ouch.