Oh my. Wouldn't we feel stupid if that were the case.100000 years of travel at current tech according to a local news report. Which means if we are at the point where we need to leave this junkball, there might be nothing left there when we get there.
They have some way of doing it, but not fully researched - VacuumThen we must invent artificial gravity technology for space ships.
They have some way of doing it, but not fully researched - Vacuum
About the speed - if i recall correctly you gain speed from moment to moment in space (something what comets do) - so firing yourself with some enormous speed would be solution - you would gain speed all the time so maybe to get to that planet wont be sooo long
Problems are firstly breaks - you will land there and become like a Pie or gravity from other planets could slow/faster you or change your course
What about bone degradation/density?You don't gain speed, but as there is no air and hence no friction, you would not lose speed this assumes no force acts on you, like gravitational fields of stars and planets
You don't need artificial gravity if you work out in space, that's what astronauts do to prevent muscle degradation.