That was not the British wAy and would of required a huge expense and manpower to accomplish. Also in continental Europe people could walk away to another friendlier country or region. But what you do in Ireland when Britain controlled the ports and people not have $ to move? They would of been hArd pressed to contain revolts.
The lack of a refuge in walking distance will absolutely make the Irish resistance harder driving up the cost in British manpower and gold. Another reason why it didn't happen in OTL, but if you had an English Monarchy strong enough and determined enough that isn't necessarily an insurmountable obstacle. Remember the Flight of the Earls and the Wild Geese was with the cooperation of the Dublin administration, the Earls and the Wild Geese wanted out and the English wanted them out. Doing that on a larger scale, i.e. offering conversion, death or passage to France/Spain would strike me as a likely option that a determined English administration might take.
They kind of tried IOTL with the penal laws. About the only thing more they could do would be to start executing anybody who doesn't convert, which in turn would probably require a big and bloody Catholic rebellion resulting in an equally big and bloody government attempt to stamp out papism in the island once and for all. (They could theoretically try during peacetime, of course, but even in the 17th century killing defenceless civilians during times of peace tended to be frowned upon.)
No they didn't actually. If you compare the behaviour of the English and later British in Ireland and the Hapsburgs in Flanders and Bohemia or various German Princes after the Thirty Years War the lack of interest in conversion is notable. The Penal Laws were structured to maintain the Protestant monopoly of on power and keep the Irish as a poor labour force to available to cheaply work on the Ascendancy Estates. In contrast in Europe the first stage was the same as Ireland, the dispossession and elimination or exile of the native aristocracy and it's replacement with a new class of outsiders and opportunists (Bohemia is a good example of this) but then you saw the Crown, Church and new Landowners work in concert to enforce conversion of the remaining population. That simply didn't happen in Ireland, the Crown did have the money or the will, the Church of Ireland was a sinecure for Englishmen who frequently stayed in England and the landowners wanted quiescent workers, they didn't want to be hanging their labour force and reducing their income.
Catholicism is the faith of the Irish nation, at least in tradition (I am not bringing the 21st century in this; this is purely on historical grounds.) The more the British oppressed the Irish, the more they held on to their already very strong faith. Irish catholic tradition goes back millennium; it was strong even before British oppression. The economic oppression, such as with the absentee landlords, was incredibly immense. The Irish resisted this largely through clinging on to their culture; the only remnant left after the British takeover of the whole island. To convert to the Protestant faith to them would be to lose their Irish sensibilities and turn back on their family; their community; their people. The local pressure was immense. The Ulster Protestants would also not convert to Catholicism even if under Irish Catholic rule. The whole tragedy is full of sensitivities and many on both sides are bitter to this day.
Elizabeth tried, the Stuarts tried, Cromwell tried. Maybe you really do need a mighty ASB to convert Ireland to Anglicanism
The idea that the Catholic Irish are innately more attached to their faith than other people is rubbish, the Flemish were very attached to Calvinism but Alba, the 80 Years War and an ocean of blood changed that. If England had done to Ireland what Alba did to Flanders e.g. upon capturing a town execute all the defenders and leading citizens* and then force the survivors to publically submit to the Church, hanging those who didn't, I suspect Ireland would have as many Catholics as Flanders has Protestants today (1.4%).
*something Cromwell did twice, Alba did it to every town he took
**something Cromwell nor his predecessors and successors never did