Nice Ganner
. I don't have experience with that sort of situation, but maybe you can move your capital to somewhere in italy, pick your 2 best dutchies for yourself, create as many dutchies as you can and give them away to 1 vassel at a time. You can search easier for possible people with the Characters tab. Just scroll down to dynasty members or people with decent opinion/stats or traits. Make sure you have a good succession law so you don't lose it all
Then you can maybe start changing your primary culture to a local culture. Just make your dynasty members have Italian wards and you should end up phasing out Irish. You could ditch Ireland completely if its too much hassle as teeth said. I dunno how safe it is down there though, maybe you could keep ireland incase you get overrun by Muslims or eventually you will get a mongol horde event from the east, dunno if they can push that far
Vibe when I played Ireland England had many years of succession crises and had no allies so they didn't bother me at all. Scotland was allied with Norway but they didn't join any war against me. I found some claimants to take over larger pieces at a time. If you click de jure dutchies tab on the bottom right, find a large dutchy in scotland or Wales, select the county tab, then tick de jure, then click the Dutchy tab, then click claimants. See if theres anyone with a thumbs up for the dutchy. You can then invite him to court, make him your vassel (give him a county or holding), then you should be able to go to war for his claim and end up with him as your duke with his land after the war. Thats how I took over wales, scotland and Brittany for the most part iirc. Might have fabricated some and created or usurped some dutchies. You can also use claimants that don't have a thumbs up by marrying matrilineally to them so they come to your court. If you do that with your dynasty members you might get claims for their sons too.
Pretty much all game i've had minimal levies set in the laws, but ive put taxes high and crown authority I've ended up with at max atm. I have 10% feudal vassel tax. Its not much, but for places like Brittany its still bringing in a lot of gold. If you have decent tax income you can build up gold then use mercs if you need more troops for a war. Upgrade the castles you own for more troops too. I control Munster and Tyrone I believe, the 2 with the most counties. But I gave away Ormond because otherwise it only generates 25% of its gold I believe because its a city as capital. You still get about the same income from taxes by giving it away but at least the vassel can then upgrade it rather than waste the gold