Any advice on the oil?

Which engine do you have in your Jimny? Check the valve clearances if you're concerned.

Oil is supposed to get hot. The air under your bonnet will also get hot. Neither are a problem. Also 4krpm is nothing, they will sit at 5k all day long. And they will go around corners without oil starvation. Look at the sump design. The pickup is in that deep bowl at the back. There's no way it's getting starved of oil.
I've raced mine on an oval flat track without any issues. I've also done ~400 mile trips at 85mph without any issues. And I regularly see 6,000rpm in 3rd gear to maintain 60mph towing my 1,200kg trailer up hills, again no issues.

Don't over think it! Do your rallying and learn as you go. You'll soon realise that you should have put this effort into the suspension and drivetrain, and not worried about the engine.
 

the jimny is a 2000 model has 144k kms, but the engine (non-VVT M13A 5 speed manual) was rebuilt (i think) 6 years ago because my gran (it was her car) ran it with no oil and grenaded the engine, i don't know if the engine was swapped or if they just resleeved the cylinders, my gran doesn't remember and to be honest that mechanic was an idiot and did more harm than good to the poor thing.
also yeah i should have the valve clearances checked, my new mechanic told me that it could be the problem (and i think so too since they haven't been checked in forever).
also, right now the car is sitting in the shop because they're swapping my old dampeners for reinforced offroad ones and repairing the steering box since it's almost completely broken.
as for the oil, would an oil cooler be useful? and i'll make some vents in the hood i guess, i wanted to keep it looking as stock as possible on the outside but form comes second IMO

I stand with what Busta said
Put a lot more time and money into suspension set up
Something like a Dave Marsh Racing jimny kit 
Just push the engine till it blows...........you will be surprised how much abuse the M series will take 

well ok then, i'll push it till it can't push anymore XD responsibly obviously
and i'll check that racing kit, thanks for all the help guys

Sounds like your problems are to do with the engine's previous history. As Jack says, push it until it gives up. Then fit a good engine. Go for a 1.6 if you have Suzuki Lianas in Italy. They should be cheap and it's an easy way to gain power. An original engine with regular oil in it, serviced according to the service schedule will do everything you want.
You won't gain anything from putting holes in the bonnet, or fitting an oil cooler. Spend money on things that will make it a better rally car, such as a Quaife diff and the lightest wheels you can find.

If you're on FB

www.facebook.com/100057667290318/videos/621798978536237

ok so, i asked my mechanic and he discussed my valve clearance situation with other mechanics and all of them say that my engine run perfectly.
so i might just be a little bit paranoid about the car XD

I reccomend more time driving and less time guessing what might go wrong

i got the car back today and the new suspension feels pretty good already, also i noticed the oil temps are pretty high after a little bit in the high revs but they never go over 120 C so i guess that the engine won't suffer, next mod will be an oil pressure sensor
also, just out of curiosity, how much power can an m13a with stock internals handle?

You do need a thermostat controlled oil cooler at that oil temperature.

Drain the oil and get a used oil analysis and post the results here of the UOA. How many miles has the oil been in the engine?

I'm not convinced about the depth of the oil pickup but it was say 10 years ago I changed our 2007 sump so would need to see it again

I believe you probably need some sump mods to stop oil starvation if what you are saying about your rallying is correct.

There is no doubt in my mind that your engine is worn.

If you have a temperatures of say -30C in winter you need either a 0Wxx or 5Wxx oil for those cold starts not a 10W.xx

What oil do you use?

You obviously do not understand that the gauges in a production car are part of the in car entertainment system and they are not accurate.

You need accurate oil and water temperature gauges, the oil is part of the cooling system as well as the water in your radiator especially at high revs that you report. You need an accurate oil pressure gauge.

Let's get that oil temperature down to100C for your next engine. Start doing that now for when that engine lets go and it will.

The engine was rebuilt idk how many Kms ago because my nan ran it without oil and destroyed it.
the oil was changed 3k Kms ago, and the oil temp gauge I have is aftermarket, not Stock, the oil is 10w30 and the lowest the temps get where I live is -10 c if it's really cold, also the lateral Gs I pull when rallying are not enough to starve the engine, and the oil is not shiny in any metallic kind of way so no problem about that.
The engine was rebuilt less than 80k Kms ago (I'm just guessing, my nan doesn't remember)
The thing is, the water temp isn't that high, the water gauge doesn't budge from the center and the radiator hoses coming out of the engine are hot but not too hot to the touch, while the aftermarket oil gauge needle point to 120 C (for example), the sensor is positioned in a sandwich plate for the oil filter. My doubt is that the sensor or the gauge weren't installed correctly and show a higher temp than what's really there.