The indications provided on the IP-1310 display from the RWR and MWS are the only in cockpit indications you'll get from which you can deduce the threat type. However it can only provide you with limited information.
The RWR will be able to identify the type of system that is/is attempting to engage you, but all the MWS can do is tell you there is a missle in the air and where it is in relation to your aircraft. It's up to you to decide on the type of threat the MWS is indicating based on other factors such as any other indications from the RWR, known threats from the briefing/you've spotted yourself or friendly air or ground forces engaging other targets.
In summary, if the RWR produces and indication with type, then you know the system type already so act accordingly. For MWS indications a bit of pilot assement is required, so make sure you read the briefing and take note of any known threats and their locations so you're not suprised and be sure to build up and maintain a high level of situational awareness. In addition, be sure to read up on all the systems featured in the sim. Start by reading up on a system in the sim's encylopeadia and then head off to google and read up on the systems capabilities (the in sim encylopeadia only has very limited information). Once you learn and understand the threats you'll be far better placed to deal with them.
Indeed, but if you are in any doubt as to the system type, employ a mix program. It's far, far better to have to RTB due to having expended all your consumable countermeasures than find yourself spiraling to the ground in flames after being hit while trying to "conserve" consumables.
Remember: Flares and chaff bundles in the dispensers are worthless after you've been hit. Don't be scared to use them.
Yes and no. Missiles generally fly either lead persuit (using proportional guidance) or pure persuit (essentially following the target) , there are IR and RADAR guided missiles that fly each type of intercept.
Not at all. In fact IR guided systems are by far the most numerous on the battlefield. Even a long range RADAR SAM site such as SA-10 or SA-11 will have a large number of short range IR guided systems protecting it.
NB: In DCS some mission designers will build realistic SAM sites with several layers of defence, others won't and will just place one or two launchers with no supporting assets.