Starting question

Of course, so long as you constantly research online and in papers and learn from them yourself! You can never get enough help :)

TL;DR

She is not halter broke if she is disrespectful as you had posted.
A halter broke horse should do whatever it is you want on the ground, respectfully.

Back, follow, left, right, turn on the forehand/haunches, side pass, two track, leg yield, ground tie, cross tie, be able to be groomed, stand for vet/farrier/dentist and more. (showmanship patterns etc)

When your horse can do that, it is halter broke. My horse, is not halter broke - yet.

After that, I would start lunging. You do not need a round pen to do so. Just really good body language and sense of direction. When this is mastered (w/t/c/stop, back, change direction) on a loose line in a perfect circle (you do NOT pick up your feet, you simply shuffle around) then you can introduce tack.

After she will stand and lead with tack (also give to pressure on the ground from the bit), practice lunging with tack. Get back to the perfect lunge, only with tack.

THEN you can start backing her. Stepping in the stirrup, introducing weight, laying on the saddle etc.

THEN you can start training her under saddle. Which would take more than a thread to explain, let alone a post.

Hope I helped. Like I said, I didn't read the whole thread.

Yes that helps a lot thank you.

Your first step is to gather used to being with you and respecting you. I'd bring her in tie her if she ties brush her have a play with her feet, even just patting down legs at first if that's all she'll cope with.

Then do some leading work, walking trotting yeilding exploring areas as she's comfortable. When she takes brushing like an old hand get her used to a saddle blanket going on and off

When she is fine with it on and off introduce an elastic surcingle or go straight to a saddle

Continue with your usual walking trotting yielding session

Once comfortable with all that I'd introduce lunging. I find it easier without a round yard as I can move with the horse.

I find lunging vitally important. Ella had her 4th ride today. I won't get on unless she can canter and jump on the lunge and come back to a calm walk. I get on and she's quiet as a lamb.

This is a very brief explanation I hope it makes sense

Your brother in law sounds as though he may prove problems good luck though!