You can always change the level of which you start the war at in the camp menu. And as for companion recruitment, I assume you mean that you need to gain rank. An easy way to do so is to constantly do a task for either a lord or one of the local authorities of a town. I honestly find the latter not only quicker to do, but they usually also give more rank points and influence, plus a quest from one of them is almost guaranteed to give faction strength, once the war starts that is.

I am not able to recruit more than one companion, even though I have the requisite rank and influence. How can I fix this? Can I as a rohan player recruit elven companions?

引用自 Novax Djocovid：

Can I as a rohan player recruit elven companions?

Each faction has its own Rank and Influence. It doesn't matter how much rank or influence you have with the Rohirrim; you need to gain rank and influence with the various Elf factions before you can recruit their companions.