Long story short, the flooring installer I was using was taking days longer to finish the install and coat. I told it had to be done that day (I was sick of his excuses) and he took all of his tools, some of my material (hardener for the Bona sealer) when I was not on site and will not answer his phone or Texts and has not been back. This happened Thursday mid day.

Now I am going to finish it myself. He trowel filled the floors for the low spots and now you can see the filler, did the heavy sanding and edging. More or less it is ready for the sealer and I am not sure what the best way to go about this is.

I don't want to see the filler at the low spots. How do I handle this?
There are a couple of spots where I see the edger dug in and left streaks, what grit sand paper should I use on my belt sander to remove these marks?
I wasn't sure if I needed the hardener or not for the Bona sealer
Do I need to rent a buffer for the in between coats or is there another method? What grit sandpaper?
I don't want to see swirls in the floor when I am done.

Any input would be greatly appreciated!

It is about 700 sq feet of 3 1/4" white oak on the 2nd floor and 250 square feet of American cherry on the 1st floor.

I understand consumers have a time line but sometimes things just take longer than expected. One thing you don't want to do is be unreasonable and push a professional to do a finish job faster than necessary. Perhaps he was going to work on those unfinished areas before he went on to the sealer/finishing part.

As an electrical contractor I know when someone is working and when someone is not working efficiently. You won't get much done if you show up at 11am when you say you will be there at 6am and take 4 hour lunch breaks. He said that he would have 4 experienced workers with him and it turned out to be him and a rookie that kept doing things improperly and had to be fixed. He kept saying how he was a perfectionist and I had to keep pointing out things that were done wrong.

I had to take all of the treads and risers that they installed. They used 16 and 8 penny nails to secure the treads down and didn't use any glue (thank god otherwise I would not be able to get them off without damaging them more) There were gaps between the top of the riser and bottom of the treads where you could see the stair stringers. The risers were not even cut the same length. They were not plumb or level either.

Among other issues they took a day and a half to remove the old stair treads and risers and put 3 huge holes in the walls in the progress.

This was not a hard working professional contractor who ran into problems, this was a poor contractor who did not manage their time correctly.

He kept saying that he was ready to seal it, but there are tons of spots where you can see the filler (I hate seeing that) how do I go about removing those spots?

Well you should have said that in the first breath. Anytime your posting around professionals of the same trade we give them the benefit of the doubt. You know how lots of consumers are. Course a sparky's work usually cannot be seen.

I'd say that floor needs a good sanding with the big machine, start all over.

I should have said all of that in my 1st post (just too much to type)

ZING!
Although most of my work is exposed in commercial/industrial jobs I am picking up what you are putting down.

Today and yesterday I rented a square buffer from HD and it got most of the of the filler out and edger marks. Luckily my dad who is a lifetime wood worker (and actual perfectionist unlike this other yahoo) has been helping me. He was getting out all of the other stuff the square buffer did not.

We should be set for sealing tomorrow. I am going natural and not staining.

Any tips for a someone who has not sealed a floor before?

In order to finish your word you should focus on your goal. If that contractors left , you hire a new one. If you have the equipment you can do it by your self, or you can buy a electrical contractors.