Too much timing???

Yes, no,and maybe.
YellowRose spent a good deal of time, giving you advice, and it's all good stuff.
My two-bits will get you down the road without blowing up the engine.
I would drive it a few hundred miles and get to know the engine. If it is 2 or 3 or4 degrees short of optimum,at WOT, you might not notice it. It kindof depends on your driving style. What I mean is, how often are you at WOT compared to just cruising around? Getting to know her, she will have a chance to tell you if she's happy under other load situations. Then maybe you can increase the initial timing, and or increase power timing or play with the rate of advance. Don't be in a hurry to slam the big numbers.
And I cannot stress this next statement enough; The vacuum advance unit can be your engines best friend, at low to moderate throttle settings, that produce manifold vacuum over about 12 to 14 inches to as high as it goes. As soon as you have the idle to 3500 timing bugged out, try to get that puppy on line.
I live at 900ft and on a huge flat plain,hundreds of miles wide. And so does every car I have ever tuned. So I can't help with altitude questions.