Thawing fish in a plastic bag can work. Put the bag in a large bowl, add water. Or even not, but water, being denser than air conducts heat better. Tap water temps are best. Some warmth to the water when first beginning thawing is ok, if there's more than say -- a pound of fish to thaw? The water will get cold to the touch fairly quickly. Normal 'cold' tap water can suffice. With the pacaged frozen tilapia I have bought recently (each fillet in it's own sealed plastic, many of those to one larger bag) I thaw them in water when quick-thawing, even though the package says don't do that.
If the fish is too mushy -- try some other kind of fish next time around? I dunno... too many variables...
Salmon may be high in iron? I do favor the Pacific kind over the farm raised Atlantic.
Pacific King salmon (chinook) especially...but info I'm reading now indicates spinach to have 1.7X iron content than most tuna and salmon.
In descending order of favoritism from Kings; Red salmon (sockeye, often canned, but costs a lot more than pink salmon), Silver salmon (coho) sometimes seen in fish markets and grocery stores, but relatively seldom, Dog salmon (chum) no often marketed nationwide, and of course there's the ubiquitous pink salmon (humpies) in the can. The kings are $ure high in co$t though. But fresh king salmon on a smokey barbecue -- oh, yeah.
I don't know if swordfish steaks are high in iron (they might be) but they can be high in mercury. Some of that heavy metal stuff, you know? I hear big tunas can be high in mercury (it varies from fish to fish, depending on where they've been all their lives, I think).
Just now I went looking for nutritional info for tuna. That would vary depending on type, but then still be somewhat comparable to one another at the same time.
I'm not recommending Starkist as some kind of "better" canned tuna. It's not, really -- I used to favor Bumble Bee because West Coast fisherman sold albacore to Bumble Bee for decades after Starkist pretty much went away, and didn't transship from the West Coast to wherever they had canneries. BUT Starkist has a web page on 'solid white' albacore. Iron levels, expressed as percentage (of daily recommended allowance I assume) are low at 2% for about half a five ounce can, but are high for Selenium -- 70% -- which you may be a bit low in also?
For albacore in the can, if not satisfied with the normal Starkist/ Bumble Bee / whatever brand X import, I can recommend the canned albacore at Whole Foods. Last I bought it I could get a 5 ounce can (in water) for about $2 --=maybe $2.50. The tuna packed in oil would be about $4. Why that much difference, I do not know? High quality olive oil maybe? BUT -- the fish come from American hook-and-line tuna fisherman -- most all the tuna was bled and blast frozen at sea (instead of brine frozen -- which can add salt) and each can is labeled on the bottom for what boat it supposedly came from.
Too much info. Sorry. Fetching iron content info for farmed tilapia, and catfish may have been a better use of my time, and yours.
I do wonder though, about trace minerals possibly associated with iron, and iron deficiency. In the back of my mind -- it seems I've run across mentions of something along those lines, sort-of comparable to how calcium uptake can be dependent upon presence of magnesium, and vitamin D.
Have your husband research it for you? You've got bucolic Lutherans in Ohio to go visit.
Iowa, I meant. Although there's maybe a Lutheran with the real deal braunschweiger in Ohio too? There's gotta' be, somewhere.