Peter,

They are all good factors to be considered, with some reservation.
I'm not going into much detail, there were books written about the subject, just want to give you some idea, I'm using.

Last start finishing position, what value do you put on a 10 len. third in a 6 horse race?

Beaten len. is important, BUT only in conjunction with the class of race and distance + number of runners, it tells you a lot about the horse's form, fitness.

win and place % alone are utterly meaningless, I can point out some horses with 90% place and 50% win, and take them even to a moderate city meeting and they will fail hopelessly.

Weight in my opinion is only important as far as the weight carrying ability of the horse is concerned, once you know that beyond a certain weight it can't win, that's it. Of course you have to compare ALL the horses in the race and then you can give advantage to those with lesser weight.

Weight above limit is misleading, again in my opinion, because the handicapper is badly handicapped by the lower and upper weight limits,
some horses would not have a chance even with the limit weight while the top horse should carry more.

Last 3 or 5 start, I use both, rely on the last 3 to 90% but I look at the last two years to confirm.
This I consider together with the days to last start.

fitness patterns: I have both of the author's (Peter Bent I think) books on this subject, and must admit I couldn't make any sense of it, of course it may just be that I'm a bit slow on the uptake, same as with time rating.

Regarding racing patterns, I studied them for some time and again couldn't make any use of it, I think for the simple reason that horses hardly ever race in the same class or distance every preparations in the same order.

Anyway, these are just a few thoughts, as I said there are many good books about it.

Good luck