Alright, first the squat. That's a perfect Olympic squat as far as form and depth. I'd keep my hand placement closer though and not out at the plates. There is nothing wrong at all with the squat itself, just keep progressively getting stronger and training your core.
The bench. Chambewy is right that you should stay generally tighter. It is good that you tuck your elbows rather than flare tham, that's the correct way to do it. You just looked a little relaxed on the bench in the video, keep your body tighter, flex the lats and upper back.
As far as arching, here is how I feel. I slight arch is okay, as far as big arches and leg drive, that is competitive powerlifting, the goal is to maximize leverages to lift the most weight over the shortest possible range of motion within the legal limits of the federation.....I don't bench like that because I'm not a powerlifter. Your general setup is perfect for an athlete, strength sthletes like fottball players, throwers, wrestlers (real wrestlers, lol) should be coached to bench closer to what you were doing.....a closer grip, flatter back, no leg drive, etc etc.....it just comes down to what you're training for. Powerlifters and throwers for example sometimes get a little friendly ribbing going back and forth about how the one another bench, it's all good, just depends on the goals.....again, if you don't want to compete in powerlifting, your bench is more ideal as it is now form-wise, just stay tighter, you look like you're having a jolly good time on the bench, don't be so loose.
Here we go....the deadlift. Again, for the non-powerlifter, conventional stance as you are doing is the only way to deadlift as far as I am concerned. The problem I'll adress (and bear with me through the whole thing, and some people may disagree with my DL philosophy) is that you lock the knees out too soon and straight-leg it. Now, that is not 'ideal' and wouldn't be taught as how t odeadlift, BUT, some of the strongest pullers in the world deadlift MUCH, MUCH less ideally than you do. I don't know if you're familiar with Juoko Ahola, he won the ESPN/MetRx World's Strongest Man contest 2 or 3 times in the late-90's. There is a video of him floating around on the internet where he is pulling high 700's for a triple, it is something like 775 or 790 or something for a triple. Now, most observers would cringe at his form, he practically does SLDLs, but when you look at his conditioning and the development of his erectors, you can see there is no way this guy is going to hurt himself deadlifting. Same deal for a lot of the world's best pullers using less than textbook form.
The DL is more of a lift for natural pullers than anything else. If you're built to pull, you're built to pull. A natural deadlifter finds the mechanics for their body naturally. You are built like a natural deadlifter, very long-armed, with perfect leverages for the lift. My gut instinct tells me that you're a natural puller who the lift will come easy for, and you will naturally pull the best way for your body.
Now, all that said, you want to ideally pull more textbook at this point, but don't beat yourself up over it. Try to make a conscious effort to get down better at the start and do not lock the knees out so soon. The DL is one of those lifts where you can never lift truly big weights without slight breaks in form.....John Basedow demonstrates perfect DL technique for example, but he uses weenie weights, watch the WSM and you'll see technique that you wouldn't want in a physiology text, but you'll see huge lifts done safely....My honest opinion is that you should definitely try to make sure you don't lock the knees out so soon, but don't get so cray that you stall your progress and back down to sissy weights trying to acheive the 'textbook' deadlift, when the words textbook deadlift and big deadlift almost never appear all together. Just keep the bar close to your body, and don't hitch, and I can't see you getting hurt if your erectors and abs are up to snuff and you don't use weights you clearly aren't ready for (ie, don't try 5 plates next week).
Train those erectors and abs, get a STRONG core and try your best not to lock out the knees so soon, but overall deadlifting is a beast unto itself.
Also, I suggest you PM Glenn Pendlay and ask his thoughts on it, I'd respect his opinion on the matter more than anybody's.
But, thats my input. Squat is perfect, get the hands closer.....for a a non-PL the bench is fine, but get damn tighter, and on the DL try to use better form in regard to locking out the knees too soon, but don't take the bar weight down to 225 in order to acheive 'fitness geek' form.
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If you were tight, you'd lean way forward or just not go as deep. That's what I think, anyway.
