I am afraid Kat that you have enumerated most of the contemporary and indeed subsequent reasons advanced by British Politicians and Whig Historians to justify British Government policies that allowed and compounded the horrors of mass starvation in Ireland to proceed unchecked.
Regarding deaths at sea, if you place ill people in close confinement with other who are starving you will generally and geometrically increase deaths!
Why, even that A + B = C was realised by the vilest breed of humanity seen on this planet, the Slave Traders.
Although their method of mitigating disease in their ‘cargo’ is scarcely creditable to modern ears.
They simply threw the ill or the weak overboard!
Rather as the British Colonial Power threw the Irish Nation overboard during the Great Famine.
By backing the Great Landlords with all the forces of the military against the most marginalised, those male and female landless agricultural labourers, who made up the pool of seasonal labour.
Each Spailpín Fánach life precariously had depended on the pennies they earned as Migrant Labourers during the planting and harvest.
Break that Cycle and you broke their lives.
Today of course we simply cannot conceive of or understand the British Colonial mindset.
Our lack of understanding is to our credit, rather than theirs, I may add.
To routinely brutalise the population of their neighbouring Island, as they did, demonstrated unfathomable cruelty.
A Sin against God.
It also ran contrary to economic sense!
A Sin against Mammon too, that they could more easily understand, but did not!
Intriguingly a prosperous Ireland within a political Union would have calmed nationalist sentiment.
But British Beggar thy Neighbour Economic Policies routinely destroyed any shoots of industrialisation in Ireland.
Making Ireland poorer.
Damning it to a dependence upon Agriculture.
Reducing the majority to either 9 Month-at-Will Tenant Farmers or an aimless existence as depressed Day Labourer.
This unfathomable cruelty without even a skein of rationality of course marks out an unusually sadistic and morally bankrupt nation, whose concepts of Superior Worth was aeons removed from the Superior Sort of Christianity they thought they professed.
Their scale of values then were, and still are, topped by their monarchy, and by degrees descending to the most destitute Englishman.
And by a greater remove to those captives of their British Empire.
Those Captives measured in worth by an imposed Class System, but each infinitably of less worth than the poorest Englishman!
A definition then of 'Englishman' might graciously include the Welsh and less graciously exclude Scottish Highlanders.
And women of all those nations were of course routinely ignored, despite a woman sitting on their throne!
All this partiality of neglect fuelled a fervent desire to be rid of Britain and its Union!
And of course that sentiment naturally targeted those Landlords and Land Agents within sight or reach.
They were the local cogs of an Empire that ground Ireland’s People.
Which of course sealed the fate of Dennis Mahon and many others.
Poet Rudyard Kipling, born 20 years after the Great Irish Famine, wrote an explanation of the how the treatment wielded by Dennis Mahon and myriad others of like-mindset to their starving Tenants was not only tolerated but applauded by the British Government and their Upper Crust.
Kipling’s 7 Stark Lines relieves me of a necessity to write 700 or 7000 Lines explaining the enormity of the British Empire’s Crimes Against Basic Humanity in a Famine-ridden Ireland to a modern Audience.
You may ‘smell’ the smug assurance within these Lines of a People ‘destined’ to Rule through a combination of Military Might and a Shallow Conscience.
“The White Man’s Burden”
Take up the White Man’s burden–
Send forth the best ye breed–
Go, bind your sons to exile
To serve your captives’ need;
On fluttered folk and wild–
Your new-caught sullen peoples,
Half devil and half child.
Certainly, that poem was written a half century later  and addressed to the United States, urging them to seize colonial control of the Filipino people and their country.
But it demonstrates the continued belief and willingness of Britain’s ‘Elite’ to snatch lands and wealth from peoples who were 'iinferior' or unable to resist.
And having snatched those Nations from its native ‘Children’ there was no sense of a ‘parental responsibility’ in times of sickness and misfortunes, such as a Government of their own might demonstrate.
The precise cause of the Potato Famine, Phytophthora Infestans fungus, was beyond human influence.
The Great Hunger which followed was a result of human indifference and an imposed Landlord and Class System that put no value upon the ordinary Irish people.
The Sentiment of the Starving bettering their condition by forced migration, or more likely dying in the that attempt, has a whiff of Ben Carson’s mis-speak.
Remember, he announcing to a room packed with hundreds of federal workers that the Africans captured, sold and transported to America against their will had the same hopes and dreams as early immigrants!!.
.As Homer Simpson would remark…. “Volunteering is for suckers. Did you know that volunteers don’t even get paid for the stuff they do?”
To end upon a reconciliatory Note, I might quote William Makepeace Thackeray’s 'End Note' from his novel 'Barry Lyndon'.
Although a change of monarch from German George to Famine Queen is needed: -
"It was in the reign of [Queen Victoria] that the aforesaid personages lived and quarrelled, good or bad, handsome or ugly, rich or poor, they are all equal now."
And might I suggest reading the harrowing lines of one of the several translation versions of the poem An Spailpín Fánach [Wandering Landless Labourer].
This will explain their simple lives and desires, and finally burning rage.
It was their community that bore the major share of famine deaths.
Their simple life denied, their loved ones starved to death before them, those who endured famine and coffin ships bred a generational enmity and hatred that persists today.
Although that Past is past, it must be remembered, lest history repeat itself at some future and unguarded moment.
As Bonnie Greer drolly remarked, when Priti Sushil Patel invoked a new Famine to bring Ireland to heel during Brexit, “You don’t mess with the Irish!”.
Michael GA Dixon