The horse wasn’t whipped repeatedly. Jockeys often wave the whip which might appear to be making contact but it is not. There are strict rules about whip use, and to reiterate, the racing whip isn’t a riding crop - it’s padded foam and not painful.
Four horses fell in the race, with a number more unseating the jockey, but many also pulled up when their chance had gone or they became tired - would you prefer the jockeys kept them going to try to achieve a greater number of finishers?
Horses also don’t die in the National every year.
The jumps aren’t actually particularly high. They’re constructed from soft brush unlike standard steeplechase fences, and are quite forgiving as horses can jump through them. The lower they are made, the more likely horses will jump them at speed, so lowering them may actually make the race more dangerous.
I do agree that lowering the numbers to 30 would be sensible. There are rules for qualification and there are few horses running now who have no chance at all compared to, say, 20 years ago, but it is a large field and the issues at the early fences this year (not helped by the rushed start) would be lessened with fewer horses.
I do understand why people are against horse racing and I accept more can be done in terms of some welfare issues, but there are often a lot of factual inaccuracies quoted which doesn’t help.