I was in an age gap marriage. At least I had the protection of marriage and my husband made sure that he made his will in my favour.
I did finish up as his carer and was the main breadwinner for most of our 27 yr marriage. He had adult children from his first marriage. They received their legal rights according to Scots law, plus a bit extra. I also gave his only grandchild what he wanted me to pass on. (I wasn't the OW. His ex is currently with her 4th partner, if you include my husband.)
All my husband's care needs fell to me. At one point, I was working full time, caring for him and both my parents. (Though my parents were in their own home with carers going in, in addition to my input.)
He had to have major heart surgery. I was driving to work each day, driving over an hour to the hospital to see my husband, driving over an hour to my parents to check on them each day. Sorting out necessary shopping for all afterwards. (Good job there are 24 hr supermarkets.)
The adult children actually cancelled a planned visit: "There's no point in coming up to see him when he's in hospital. We'll come up later in the year when he's back home."
God help me, I fell asleep at the wheel of the car one evening. Only momentarily, but it could have been catastrophic. I took one day off from hospital visiting the next day.
What I'm trying to articulate is that I had a husband who loved me very much. Of course I did that for him. You never know what life is going to throw at you...
Two years later, DH had a major stroke. I worked for another 5 yrs, but then finished up quitting work two years early. It's had a significant impact on my pension and standard of living.
If your partner doesn't respect you enough to marry you and to make sure that you're taken care of financially, OP, I'd walk. It's hard being a carer. With no protection...Well, I'd find that a slap in the face.