My advice as per your brief:
1. Yes you can challenge the decision of High Court in Supreme Court.
2. You need to find merits according to your case as those merits will be your grounds for an appeal.
3. You can take grounds regarding your health, work, taking care of parents, illness of parents, witnesses and their city, your wife has place to stay during her visit to pune for hearings, you can offer her accommodation expenses during her visit for hearing to pune, that pune is well connected to Nanded etc.
4. Cost depends upon the lawyer you hire for your case. In SC people mostly engage a briefing and drafting lawyer who’ll take care of drafting, filing and briefing. Further for arguments you can engage a senior Advocate who has good face value because in such cases that leaves a huge impact on the outcome.
5. Average cost for drafting, filing and briefing is around 1lac. Further if you want to heir a senior Advocate then it depends upon whom you chose.(starts from 50,00/- to 2,00,000/-) in such matters per hearing.
Any assistance sort in your above matter please feel free to consult.
Regards