IMHO its normal not to be able to combine the largest rear gear with the largest front gear. That makes for a pretty jacked up chain line and usually ends up with the upper jockey wheel on your rear dr meshing with the cassette. if you need that low of a gear while riding shift the front dr to the middle ring.

Two points, if your chain is rusty and gummed up with grime, it won't shift properly, you will never be able to get it to shift normally without cleaning it first. in fact that may be part of the problem in the first place.

Secondly, I had a very hard time tuning the dr on my mt. bike because as it turns out I had a bent dr hanger. which meant that no matter what I did, nothing was lined up properly. In my case it was $5 bucks to have the LBS straighten it out, but if you don't want to spend that cash then you may just have to deal with a bike that doesn't shift perfectly.