Answering your questions in the order you have raised it
1. Claims ratio: Yes, one of the important things to be checked is the claim settlement ratio. It gives an idea of how much difficult or how easy it is for the family to get the insured sum when the primary insured is unfortunately no more.It gives you the realistic figures of families who have applied and got the claim settled (the money in their hands).
It's also useful to see the claims pending also. You can check many websites that compare many popular companies or check the IRDA(Insurance Regulatory and Development Authority) website directly. For instance ( claim settlement - LIC(98%)).
2.online or agent: The traditional concept is that an agent is a physical person we can relate to and we will in the same region. The current concept is there are so many companies and so many agents jump from company to company, at the time of need the agent has either left the company or is no more useful to us. Once the family has relevant details, then the settlement is usually not an issue unless there is foul play or a suspicious death or hidden illnesses.
Buying it online makes it easier and relatively economical. Online premiums can be anywhere between 10-25% cheaper than offline policies. As long as you choose a good company, then things should be fine. In case a company cheats then people can take the effective route of shaming the company in the media and local papers if the claim is genuine and money is not being given.
3. how much to take: This is a question that has many parameters to be accounted into before deciding. One can option from 1 lakh to few crores but the key is to have the adequate salary or accounted income declared to give some idea that one will be able to pay the premiums annually.
A lot of people mistake a term policy for an investment.It is not, it's what the family needs in the absence of the head or earn member. It depends on the family's needs, needs for long-term payments, assets that the family hold, salary of the insured person, inflation and growth rates of the country etc.In general, advisors suggest 8-10 times the average salary earned as the sum to be insured for. You can again check this with your circumstances from many websites that have term insurance sum calculator ( moneycontrol.com is one).
If you still have doubts, then seek a known person who can guide you and then take a second opinion before taking the policy. Whatever you do, please do it before you next birthday as the premium meter jumps up significantly as your age goes up.