//1. Should a PA specifically intended for purchasing a property be adjudicated? //
Any Power of Attorney executed abroad has to be necessarily authenticated/ adjudicated before concerned SRO in India.
//2. Should my son execute a new PA in my favour or in favour his close relative, such as his brother-in-law who is a citizen and resident of India?//
In case of purchase of immovable property, the purchaser/principal has to be resident indian. In case, purchaser is NRI, then certaun rules are prescribed by RBI to be complied with. In your case, you are only agent and the purchaser is your son who is indian citizen. There is no such restriction on an OCI being an agent. Therefore no new power is required.
//3. Should the PA be attested by the Indian Embassy in Sweden or is it sufficient to have it notarized in Sweden. Attestation by the Embassy is time-consuming and involves a trip to Stockholm from Gothnburg, a distance of some 500 kms. We would prefer notarization in Gothenburg.//
Law prescribes either attestation by embassy or notarisation. Both has equal value. Attestation by embassy is not madatory. Only an alternative. Notarisation will serve the purpose as per section 85 of Indian Evidence Act.