Your schematic looks OK. However, it is important that all the little details are also done correctly.
OIL-LINES - The most important oil-line to get right is the feed-line from external-tank to main-pressure-pump. Given that the main-pump has to SUCK oil through this line, the line should be as short as possible, and have a large enough diameter to give low restriction. My guess is that your AN-12 line is big enough, but maybe try to make it shorter (see below...).
It is also very important to check that this flexible oil-line is not so flexible that it gets flattened out by the suction, and so blocks-off the flow. This "flattening under suction" is a very common problem on the suction side of water cooling lines. The flattening-under-suction is more likely on the inside of tight bends of the line, so check this.
Also make sure that there is no joint in this line that allows air to get sucked into it. It seems that your main-pump-suction-line attaches to the sump as an AN-hose, and then I guess there is a gallery up through the sump that mates to another gallery in the engine-block, that then leads to the inlet of the main-pump? Make sure that none of these mating joints can allow air to get sucked into the line. So "O-rings" or "gasket-goo" may be needed.
The other lines, from sump to scavenge-pumps, then to external-tank, should be OK. They could be smaller, but no problem as is.
EXTERNAL-TANK (aka "Swirl-Pot") - Your tank is tall and narrow, which is good. (I originally worried that you made a low and wide tank, which would be worse than the original wet-sump.) Standing the tank up vertically, rather than at the slope you have it, would be better (see why below). An even taller tank would be even better, perhaps with the upper section of smaller diameter.
Your infeed to the tank is done correctly, being tangential to the circular tank, which gives the swirl that helps separate air-bubbles from oil. A smaller diameter hose/inlet-nozzle here, and a smaller diameter of tank, would give much increased swirl and so even better air-oil separation. But maybe OK as is.
I think your biggest problem is at the bottom of the tank. The times that the engine-bearings most need a good supply of oil is when the throttle is wide open (WOT) and engine is spinning fast. So typically during hard longitudinal acceleration. Under these circumstances any fluids in any tanks are sloshed to the REAR of the tank. So the fact that your main-pressure-pump is sucking from the FRONTMOST point of the tank is BAD. The rearward leaning tank also makes this worse.
Furthermore, looking in plan-view, your tank-inlet swirls the oil in an anti-clockwise direction. The tank-outlet should take advantage of this, but your outlet is better suited to picking up CW flow.
So one "quick-fix" would be to relocate the tank-outlet (ie. suction-line to main-pump) to the rearmost point of the tank, but still close to bottom of tank. So shift it from right-side to left-side of tank, as seen in your side-view photo. A vertical rear wall to the tank would also help. Also a horizontal mesh-screen/baffle, at about half-height of the tank can also help to keep the air-bubbles up top, and pure-oil down below.
BOTTOM LINE - The "... tick-tick..." sounds you heard from the engine are just as expensive whether the engine has the most exotic dry-sump system fitted, or just a bog-standard, no-cost, wet-sump. In either case the preventative cure for the "tick-tick" is usually very inexpensive in itself, being only a matter of adjusting a few details.
But figuring out those details ain't always easy!
Keep working at it.