You haven't removed the valves and on the first picture, the bottom left valve looks like something is going on there. You have to remove the valves, make sure you mark which valve goes to which hole, and you may have to hand lap them back in. Some Dykem sprayed on there, of even a Sharpie pen, will show you where leakage is occurring when you spin the valve (by hand!), the ink well not all scrap off if there is a leak. In any event, with the head off, remove the valves, get some lapping compound, a suction cut on a stick and by hand, lap down the valves till you have a nice shiny seat that matches on the valve. Get al that carbon off everything. Polish the valves with rouge and the same with the top pf the pistons. You don't want to take off metal, you want them shiny. The cylinders have to come out, losing that much oil, if the bore is straight, you might get away with slapping in a new set of stock rings, if it is worn, then you will have to bore, get new pistons, to the next bore size. When I take an engine apart, I expect the worst, and I don't skimp on anything if I decide to put it back together.