1. No specific time can be provided as it depends from case to case and from Court to Court. However it is advisable to file for custody and access at the earliest. But before filing cases, collect proof of your wife's refusal to let you avail access, be it through recording calls, messages, emails etc.
2. In my opinion, no.
3. Nothing per se can be done to prevent him from filing a false case. However, the onus will be on them to substantiate their claims so be rest assured that nothing fruitful will come out of the same as you have mentioned that no dowry was taken by you and your family. You can, however, asap file a Divorce Petition so that any Dowry case filed by them will be nothing more than a counter attack.
4. I think you mean 2019. That is too vague a probability to be commented or ascertained at this stage.
5. Your parents' should not lose more money.
6. Unless you are able to establish that the same was not gifted to her, there is very little possibility of you getting it back.
7. I would not advise you to harp much on that point as you only otherwise will be saddled with more maintenance.