Healthcare penalty should be the least of your worries. If the cost of healthcare is a financial hardship, or more than 10% of your monthly income, there is no penalty, If the premium is less than 10% of your income, unless you waste a lot of money, you should be able to afford it. At a minimum, you can afford a bronze plan. And if you are like me, and had so many write-offs that made your AGI really low, you should be eligible for a subsidy. Even my best year at fedex I would have been eligible for a silver plan at less than $100 per month. And most of the healthcare under the ACA has no deductible, so office visits, labs, x-rays, etc cost you nothing more out of pocket, except the copay. A lot of people have been scared off of getting healthcare by some of the misinformation out there. But I know that some states actively fought the ACA, and that has made it expensive in those areas.
And if you can't afford to hire someone to give you a reasonable number of days off, you are either not managing your income well, or you are grossly underpaid. Same goes for being able to plan for retirement. Those need to be included in the calculations for everyone as to whether fedex ground ISP makes any sense at all. I think many ignore the issues you have, and just look at gross cash flow. Leaving because you are underpaid makes sense, but you shouldn't need to use healthcare as a reason. For me, a bad health insurance plan before the ACA was more expensive than the good plan I got through the ACA, mostly due to my age at the time.
But of course UPS is a better choice- especially long-term.