Up until a few years ago it was the norm to prescribe Clomid/Femara for 6 months before requiring a break. Then all at once they reduced that to 3-4 months, then a break. I am fine with you guys doing it either way. I think that taking a break after 4 months is great, and at the same time I've seen enough people conceive after 6 months even on the harsher Clomid that I'm ok with that, too. Your call to make, entirely up to you.
To split the dose you would need to halve the medicine and still take it 5 days. Taking the full dose 2 or 3 days would not work as well as taking a half dose 5 days. Because the way the medicine works is by suppressing estrogen, forcing your body to basically have to "rev its engines" in order to produce the estrogen it "thinks" it needs. Then after five days, you stop the medicine while your body is still "revving" and then you make a large surge of estrogen quickly. Only "revving" for 2 or 3 days would not be as effective as somewhat suppressing the estrogen for 5 full days, even at a lower dose of medication.
I generally recommend the half-dose approach instead of fewer months at a higher dose. For starters, the full dose may be too much (especially aftr having been on the medication a few months now) and could be suppressing conception a bit, and secondy, even not at full dose it still has an effect for encouraging ovulation and also swaying pink. But it's up to you, either way can still work.
Keep in mind, about your mood and feeling like chucking it all in, that it is VERY common to be hormonally low at that point of the cycle. It happens all. the. time. that I have someone who is ready to quit at this stage of the cycle and then in a day or two they feel upbeat and normal again. It has to do with hormones and so just keep that in mind, that when making a decision about things like that, you may want to sleep on it a day or two to see if you're feeling more positive once your period arrives, or once it's over with.
If exercise prevented implantation the entire human race would have died out a long time ago. While I'm fine with you choosing to do lighter exercise in the 2WW that is not what is keeping you from conception. People get pregnant while doing heavy, intense exercise for MANY hours a day. I got my 3rd son while I was working at a dog kennel, climbing ladders, throwing around bales of hay and huge sacks of dog food, jumping off and on things, lifting 80 lbs dogs into bathtubs and things and I did it for 4-6 hours a day. The human body is just very good at getting pregnant and we just need to get the sperm to meet the egg and it knows how to do everything else.
Walking is GREAT though. I actually prefer you guys do walking because so many people get injured when doing more intense exercise. I also think that were you to do something that felt a bit more "doable" it might help you stick to it longer.
Enjoy your upcoming Christmas cheat season!! I just had coffee and Merci chocolates for lunch LOL and I regret nothing. :)