There are plenty of people who complete the Camino in shoes rather than boots. I wore boots, and would probably do so again except perhaps in summer.
On the matter of how big your pack should be, I use a calculator that factors in several variables, including your weight, season you are walking in, how resilient you might be, budget, and how many are in your party. I assume you are travelling alone. I set the calculator for spring, and the 46kg you claim to weigh. For different resilience and budget settings, one gets:
- pleasantly normal and your budget only extends to purchasing essential additions to your kit - about a 40 li pack. The weight would be around 12kg, and really at the upper level for comfortable hiking, and much more than anyone would recommend for the Camino.
- you might toughen up just a bit and bring that down to 35li, but it would still be well above a reasonable weight target.
- spend a bit more on getting good quality gear without going overboard and it comes down to 30 li.
- to get below the CSJ recommended limit of 15% of body weight, you need to get down to 25li.
- If you are the sort of ultra-light fanatic who sleeps naked on bedrock, walks barefoot and eats small animals raw, it would be possible to get down to 20li and under 10% of body weight if you were prepared to go all out on light weight gear.
Clearly you need to decide how far you are prepared to go in terms of both comfort and budget, but it seems to me that a volume target of 25li would get you into the right area in terms of pack weight. Were you to choose a larger pack (say 30li) you would need to be disciplined in your packing to to keep the weight under control.