18/2 barb/rogue questions about trap skills and evasion

[rakhtal]

I want to tr my paladin into half orc 18/2 barbarian/rogue but I cant decide on a final build.
I take rogue levels mostly for umd, because I like being self sufficient but i thought that if I'm taking them I could get some trap skills as well.

My first plan was 20str/8dex/16con/12int/8wis/8cha
This allows me with +2 int tome to max search, dd and umd, but my spot and open lock will be almost non existant, as well as my balance, and my reflex save is low

If I go 18/12/16/12/9/9 or 20/12/14/12/8/8 that gives me +2 to my reflex save but hurts either my strength or con and im not sure if it's worth getting it.
According to planer my reflex in this variant is +10 at level 20. With +6 dex item, +5 resistance and gh thats only 20 reflex save. Im not sure if it's worth it.

Other variant is 20/8/14/14/8/8 or 18/8/16/14/9/9
That would give me another skill point to put into open lock to make it viable.

So my questions are:
Is it worth raising dex to get higher reflex save?
Is it worth raising int to get another skill point?
Do I need to max dd and search or can I put some points in open lock for example, and how high my open lock should be to be somewhat usefull?
(getting +15 skill items is not a problem and I'll be able to get gh with clickies or scrolls)
I dont need those skill to be high enough to disable every trap in the game, but I dont want to discover at level 20 that I wasted tons of skill points and cant do anything anyway.

Thanks for any advice