First, jacking up half the car and then going underneath while it is running and in gear is very dangerous.

Analyzing your symptoms:
1) You recently changed fluid and/or bled your brake system, which shares fluid with the clutch master cylinder.
2) When the car is in gear, it is difficult to roll.
3) When depressing the clutch pedal, nothing happens. You cannot change gears?

Starting in the middle (2), if the car is in gear it should be difficult to roll. If you can get it into 6th gear, it should resist but still roll. That tells me your clutch and drivetrain are good.

If you bled your brake system, it is possible you introduced air to the clutch master cylinder. If you google, there are some youtube videos on how to bleed the clutch master cyclinder.

Last, it is possible you have a mechanical, not hydraulic, issue. That could be with the throw-out bearing or fork that operates the throw-out bearing. Maybe even the cable that goes from the bottom of the shifter and operates the gear selection (mine slipped and I could not put the car into any gear lower than 4th). I cannot help you with this. When my cable slipped, I took it to a shop and it was a simple fix to put it back (plus they adjusted it so that the dreaded 1st to 2nd shift was much better). Good luck.