Should i flush my Toyota Yaris 2010 2NZ-FE 1.3L motor oil after check engine and oil pressure light on?

Hello,

My car is due to motor oil and filter change as it reached 5Km (5.6Km now), i've been noticing a drecrease in the leves when i check the stick and when i drain the oil. I went to check the exhaust for white or smely fumes, but it doesn't present any of both symptoms. When i start the car, it does release some very light white fume, but it also doesn't smell like oil, more like gasoline, it fades after few minutes or seconds depending of the weather or the time the car was sitting even if the car is idling.

Context

(1st oil change)

2 years ago, i ran the car for months with a very heavy usage without any maintencance, until a day i was getting the oil pressure light/check engine light showing and few noises that seemed like bad lubrication and bad oil filter, that's when i checked the oil level and it was very low. The problem was that i was very far away from home and had to move the car to service it, i've added a little bit of oil i had back home and took the car from the far place it was before. After that i parked the car for months until i was able to replace the parts i thought were bad like oil, oil filter, air filter, spark plugs and more. I think a month later or less, i was having problems with intermetent noises coming from the carter that at first made me think the oil filter was faulty or the replacement procedure i've made was faulty (after the oil change i heard the noises, just thought they were the prolonged used of low oil, which was in part, but they went away after a few runs), that also made the oil pressure light to turn on and off as long as the noise was adutible and the car started to loose speed at the same time.

(2nd oil change)

After a week i had enough and decided to park the car again and called a mechanic to check it, explained to him the missusage of the vehicle and the after procedures. He just asked me to get a new oil filter, more motor oil and some silicone. He then took out the carter, and it had a lot of hald solid pieces that cloged the internal filter, not allowing the oil to flow sometimes (the noises), he started to get the most he could out the filter and after that he put everything together again and replaced the old oil filter and motor oil and just like that the noise and the oil pressure/check engine light disapeared.

After the 1st oil change, whenever i changed the oil the volume was always inferior to the original. That 2nd oil change still had the right amount because i didn't use the car long enough between both changes.

Until few months ago the car was just fine, until it started to halt randomly and i had to take it to 2 different people during this time.

The first one performed the usual motor oil, oil filter, throtle body and other basic components maintenance, ran a scan with his expensive tool and found nothing wrong and then i had problem with the water pump making noise which i asked him to replace and the random halt didn't go away, i then moved to another person.

I went to a very expensive auto shop, and asked for a diagnosis with their machine expecting a report mentioning few errors, they did and found nothing wrong, just my front right ABS sensor which i already knew because the ABS light was on back then.

Then the 2nd guy, again, i explained what i was experiencing with the car and he then ran a diagnosis on his own and found nothing wrong again. Then, he sugested for us to execute a step-by-step procedure starting from the ignition system then move to other parts if it wasn't sucessfull which i agreed, it turns out it was the fuel pump, dirty filter and tank (we thought so), a week later the random halt reemerged and i went back to him, he then ran another scan and found nothing, then we moved to the sensors, a cable from the sensor near the V-Belt was touching the belt and it exposed the wires, he fixed that and also asked his asssitent to remove the VVT sensor wich broke during the procedure because it was half stuck (dry oil) and probably his assistent damaged it the last time i was there because i saw him taking that same sensor and inspecting/cleaning, it also had some dry oil restin on the side of the timing belt, then proceeded to take the motor cover and voila, the gasket was stiff and half broken and had little bit of silicone (from a very old procedure to replace that gasket), the parts inside looked shiny and lubricated but in some parts you could see a thin layer of dry oil with a light yellow/brown color, which may have happened during the moment i was usng the car with very low oil.

I had to buy a new VVT and gasket, and since then the car is runing just fine, the rest that came after that was just the fuel pump going bad after a very short time of usage, which i had to replace with an used from a original scrap and now i don't have any random halt issues anymore.

As far as i can seen, maybe i was very lucky (can't tell yet) and the damage done was not permanent. But now i'm thinking again, what if the piston ring is stuck the same way the VVT sensor was? Just few days ago i've cleaned the Oil Pressure valve, there was a significant amount of sludge, but it was still moving just fine, i still need to check and maybe clean the VVT oil filter tho' but as for now i'm concerned with the piston rings. If it's stuck/dirty and burning even a small amount of oil, i'm worried it may get worse and start damaging the cylinder block. Therefore the my doubt about the flush which i also know it not a easy decision to make, since it can create a whole new series of problems on old engines like mine.