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If he can't be depended upon to care for his own child, you, as an "add-on," someone who just walked midway into this movie drama, can't expect anything better from him either.
I too lived this drama, and I also loathed an adult (28 yo) stepson. He had a variety of problems--ADD, drug dependency/dealing, previous incarceration--and his father ignored all of it. He also told me that said son was already an adult and had his own life that wouldn't interfere in our new life together.
Turned out that the old man was moving drugs and using said child--HIS OWN SON--as a mule. He treated me no better either, expecting me to $$ly underwrite their illegal enterprise--talk aboaut a "family business." I was lucky to get out before The Law came a-knocking (as they later did, I learned).
Take your cue from your beloved's behavior. However he treats his own, is how he'll treat YOU if you become his wife. Let him "man up" and take care of his previous obligations before he undertakes new ones w/you and any children you may want in your married life together. It's not fair to you, your unborn children, but especially poor Anna: that's a programmed failure in the making.
But, I gotta tell you--it ain't gonna happen w/this one.
PS Since you mention "resources," I assume that's $$, and a considerable amount; nannies and other household help don't come cheap. Are you sure it's not the potential lifestyle you see slipping away from you? Don't do it to yourself, and especially not to that child. Run, don't walk, away from this catastrophe-to-be.