I believe that North Korea could have done a lot more to prevent the flooding causing as much damage as it has and it is likely to be worried or embarrassed about the figures. In turn it is very likely that they have made the figures much smaller than they actually are in an attempt to look more competent.
Yes, North Korean authorities are probably providing as accurate figures as they can at this time. There is no reason that they would not try to provide accurate figures. The incident is not the result of government action so the government has no reason to lie about the figures for the flood.
No, the North Koreans are well known for distorting reality for the purpose of propaganda, so I doubt they are being honest now. The actual figures are probably bigger, but they are trying to portrait the leadership as capable of dealing with this kind of natural disaster. It is interesting that they admitted even figures like these. Perhaps they are trying to trying to get some foreign (Chinese) help, but still hide the true scale of the disaster.
No, North Korea is not providing accurate figures. There is no incentive for North Korea to be truthful in reporting these figures. In fact, it is in their best interest to report inaccurate information. It is very unlikely that only 60 people were killed when 44,000 people were displaced by the flooding.