Avoid it, might be too much to reach the top and it is not so safe as people say

No, Weather is too cool and climbing bit difficulty near the top of fort where no stairs.

When i went in monsoon , by 4-5 pm they started asking people to descend , dont think any night camping options are there, nvr heard of , you can do pawna lake camping though, not far away from Lohagad

Yes. Probably if you start early and take your vehicle as much higher as it is possible ( considering the traffic and weather) , then you can spend time on both the forts. But again it will depend upon how much time you take to trek. You can complete the Lohgad by 1pm and then visit visapur.

Visapur fort don’t know about parking but for lohgad there is parking available

There is a charge to go up to the fort not.... 25 ruppes for indian citizens, 300 for foreigners. This charge is converted into: someone's pocket, because the place is still unsafe and full of trash

Not Top of the fort but till the base of fort, from where steps starts to climb the fort or enter the fort

Yes, it is easily connected by vehicle, gear is not required it is simple track