Yes, the 'being cheated on by an ex' is very common in these types of men. They use it to elicit sympathy from you but also use it as a reason for why they eventually start to accuse you of cheating or expressing displeasure in you having male friends which is all done to control. The worst part is that it's often projection, so they were the ones that actually cheated (most narcs are PROLIFIC cheaters). He didnt get so good in bed by accident. They often claim to have only had a few partners but the reality is often hundreds of women as they keep several on the go at once. They are often riddled with STDs too so I would get checked out at a GUM if you haven't already done so.
The dressing nice, only spending money on himself are all big signs of narcissism. Remember that you only saw him in the lovebombing phase so you haven't really seen half of what he is capable of and have had a very lucky escape.
Their ultimate aim is control and he has shown you many aspects of this which I hope you can see more clearly now so that you can learn to spot the warning signs much quicker next time.
I know it can be so scary when you realise what you have let into your life but the majority of them do disappear after a few Hoover attempts and I think the fact that your relationship was relatively short means he will give up quickly. The worrying thing is that all sociopaths/psychopaths are narcissistic so its difficult to tell whether you are dealing with one or just a garden variety narc. I do worry about this guys intensity and delusion as most narcs are far more subtle than this guy and he could be very dangerous so blocking is very sensible.
See it this way, narcs need other people to feel like they exist and if you end the relationship before they have found new supply (narcs often line up new supply if they are planning to discard) then it will be for them like a heroin addict going without his drugs. He needs his supply fix from you which is why he is acting the way he is right now. He's desperate for a fix and is acting desperate because of it.
You should be really proud of yourself for figuring him out only 10 weeks in (I was married to one for 6 years). Dont beat yourself up for falling for his bullshit (this is a common way to feel after narc abuse) and use this experience to learn about early warning signs. Estimates are that 10% of the population are narcs and ince you learn the signs, you will see them everywhere (friends, family, work etc) and learn to cut toxic people from your life. It's the only gift narcs can give.