The best thing for removing metal fragments & powder from your oil-ways is, as you're finding out circulating hot oil round the system as you are doing. Those fragments you can see are not the worry friend, they will get caught quite easily by the filter system.
You said you replaced a cylinder liner? What was the damage to that?
If it was scored & or scuffed you will have had very hard & brittle metal particles circulating through your filter system causing damage to the crank & shells.
This is by no means assured, You may be very, very lucky.
If you check the oil pressure reading this will tell you (without any doubt) if the shells & crank are knackered 60/80lbs is about right for any crank & shells at 3500 revs. If it's less 20/35 & pressure drops very quickly with revs they're f****d.
I know not everyone can afford to just strip an engine & the costs associated with that. Although IT IS the best option at this point but at least with this method you won't be guessing.
This will fit straight in where the oil pressure switch fits on the right casing & should be left on forever after, rebuild or not
.https://www.ebay.co.uk/itm/132868607069 ... 1436.l2649
If you also want to use the pressure switch to keep the ECM happy use this as well.https://www.ebay.co.uk/itm/Universal-Oi ... 2749.l2649
All the best of luck to you Sacha. JB