Hi!
I went through another assessing body, so I don't know about how strict TRA are but from my experiences:
Do you think your hours average out at the hours worked? If so (to be honest even if not) just ask your previous employer to write you averaged that time in the letter they write. They have to include that information anyway. Holidays are normal too..25 days off +weekends and bank holidays is completely normal, not sure how it then goes if it goes over that..not sure they could say you were in full time employment if it was more?
http://www.emsaus.com/blog/what-does-my-employer-letter-of-reference-require/
For Vetassess my employer had to basically write out my job description on top of a lot of silly things so in the end he made me write it haha.
Make sure to check exactly what they need to mention for TRA!
Regarding IELTS I was annoyed I had to do it after getting my degrees from England (I'm german and french so otherwise understood the requirement), but when I did it I bumped into an english girl..teaching english. That made me feel better in its ridiculousness
If you're struggling with the tests then keep taking example ones even if it's just to see the kind of questions they ask and what is important to them.
I was really nervous after doing a couple example ones but averaged out at 8.5 and the speaking exam I was the most worried about (because I have a tendency to waffle..) I got a 9 because it was actually a question I'd already had on my practice one so was prepared for. Hopefully you'll have the same luck. It's more understanding how they work than testing your english for a lot of native speakers. Obviously some have a very poor grasp of the language despite being native, but you seem fine so just make your goal to understand exactly what they want from you (ie listening, if you didn't get an answer, under no circumstances think about it because you'll miss what's being said after)
Sorry that was so long without much info.. you could always just marry the girl I'm trying to find a visa sponsor that way haha as my occupation has special requirements to it that am unlikely to meet