You have a ton to work on.
1- you need to take the weight down alot you should be using 135 at the most for a few weeks.
2- you need to improve your glute and or hamstring flexibility
3- you need to work on keeping your back flat/ slightly arched, NOTE this is not possible without #2.
When someone has adequate flexibility to deadlift properly, a few weeks are needed to accustom yourself to the exercise, loading your glutes and pulling with a flat back. After 2/3 weeks, your strength on this exercise will go up, significantly, week after week, for several weeks. One of the keys to this is that you feel tight, strong and controlled, with the majority of the strength coming through your glutes.
There is a simple fact that many people seem to ignore. ANY compound leg exercise is IMPOSSIBLE to do properly (and by that I mean, effectively using all the major muscles of the leg in an efficient and scaleable way) until one has adequate flexibility. That means lunges, step ups, deadlifts, squats, and any derivative of those. THIS IS YOUR PROBLEM. For you right now, there is no other. Dont worry about form because you PROBABLY (ill get to this in a second) lack the flexibility to execute the proper form.
Now it is remotely possible your flexibility is fine, but you just arent putting yourself in the right position, nor are you trying to maintain a flat/arched back. These two things can look similar. Judging from the vid, I'd say you are definitely a tight hip flexor/hamstring guy. Your glutes may be ok. Many guys have tight hamstrings and hip flexors but their glutes will be fine.