How would I jar a sauce for keeping at room temperature without adding loads of vinegar or sugar?

You cannot use an oven for canning - while the oven itself can reach temperatures higher than 100 degrees C, it is difficult to get the internal temperature of the contents of the jars up to the same temperature. You'd be better off pressure canning, and @Chris_H has already shown where you can read up on the technique in the comments to the question.

It might be useful to provide a quick explanation why using an oven is not reliable. Please note that I am in no way suggesting that OP's 140C is either the correct temperature or the only condition needed for safe canning.

Assuming that your contents are capable of being heated to 140C at atmospheric pressure for now, in text-book ideal conditions (assuming perfectly conductive glass), it would take 54 minutes to heat a jar of it of 10cm diameter and 10cm tall form 100C to 140C. 30 minutes is just too short.

At atmospheric pressure inside your 140C oven, your sauce will not reach too much above 100C since it is mostly made up of water. Vapourising water keeps temperature fairly constant at that, at least initially. As more and more water is evaporated, eventually, you might reach 140C, but your sauce would also be dehydrated with a very significant reduction in volume. For practical purposes, you will not see 140C for a few hours and not before your sauce is ruined. The only way to overcome that is by raising the pressure and thus the boiling point of water. This is why sterilisation needs an autoclave or at least a good pressure cooker with as high a pressure rating as possible. In any case, I have not come across a consumer type pressure cooker that would offer 3.6 bar or 52 psi to attain 140C boiling point.

edit

@rumtscho's comment below made a good point that the 140C mentioned here seemed to suggest that it was the right temperature for canning. Just to clarify, I was using OP's temperature just to illustrate the point that it would be impossible to attain that in a common oven without pressurisation. As for the need for pH control and other important conditions for safe canning, I have not attempted to address them here.

Your sauce is not safe to can without some sort of preservative (and I know nothing about preservatives). When canning, anything that is "unknown" with regards to safety is generally considered to be unsafe as the risk factor is way too large.

To even begin to tell you if it might be safe you can, we would need a more-or-less exact recipe (dried spices are irrelevant however).

You cannot safely pH test a recipe at home as mixtures are not consistent, pH varies between batches, pH varies between individual jars of the same batch, pH can vary over time somewhat as the jars sit and pH equalizes within the jar itself.

The only safe way to can peanuts that I have found is via this method: http://nchfp.uga.edu/how/can_nuts/green_pnuts.html

This uses a pressure CANNER (not a cooker, you cannot safely can in a pressure COOKER). This is exclusively for green peanuts and I do not know how they compare to whatever kind of peanuts you are using.

The chilies, garlic and onions if fresh are low acid ingredients and thus are not safe to can unless in a pressure CANNER, or in a waterbath without being properly acidified however I suspect that properly acidifying them (essentially pickling them) would drastically change the nature of your sauce. Also, due to the peanuts and shrimp paste you would not be able to safely waterbath your recipe anyways.

I think I can summarize thusly:

• This is not safe to can in a waterbath method no mater what you do.
• As user110084 stated in their answer, you cannot can this using an oven safely.
• The peanuts in your sauce are a large unknown with regards to canning safety and there are no methods that I am aware of to can normal, non-green peanuts safely.
• The shrimp paste in your recipe would mean that you probably need to account for "shellfish" being in your recipe and can accordingly however the processing time for fish is something like 110 min (for pint jars or smaller) and that would probably over-process the rest of the sauce with regards to quality.
• The sugar content may scorch if you pressure can this sauce thus causing a quality/taste issue. It may not, but BBQ sauce used on meat sometimes can scorch in a pressure canner when canning BBQ meat so I'm extrapolating somewhat.

*I'd love to be wrong, but until I see some scientific proof then I'll just say: Please don't can the sauce. Sell it frozen or something like that.

If you want to discuss more about why it is unsafe to can, or to get a second option, there is a very SAFE and active facebook group called "Canning" full of helpful people who only advise SAFE canning methods.