Manhattan Greenway question (New York, Inwood, York: shop, safe, train)

[rlrl]

I would like to bike down the Manhattan greenway soon. I know if you go to the W end off Dyckman St past the bike shop you get to the greenway. What kind of entrance is there? Is it a decent incline or steps? I would like to avoid having to lug the bike up/down steps

Also, how long do you think it would take to bike from 252 street and Broadway in Riverdale to W 48th street? I just started biking on the streets and like it but I'm far from fast. That's about a 10-11 mile journey.

Also, if i have an emergency like a flat ( i do have a road pump) and need to take the #1 train back are the side streets leading from the greenway to the #1 train safe above 96th street? I am a New Yorker but have had no reason to go to the 100's. I do feel safe in Inwood and even Wash Hts but I don't know about the 130's and 140's

Where does the greenway leave you, around 72 street? Would I have to detour over to W End Avenue/ 11th Avenue or does the greenway go into midtown and then you make a left to go east by the ships?

Would locking my bike on say 48th street west of 8th Avenue or in that general vicinity be safe for the bike? Generally it's gotten pretty upscale around there and i would imagine thieves roaming the streets around there is pretty rare these days.

well thanks for reading all my crazy inquiries

RL