Q: Nulled Wordpress Premium Theme - how to secure yourself?

Ok, so recently I got nice premium theme, somewhere from one website with this kind of free things.
In future I want to pay and get legit one, at the moment I don't have a money while the business doesn't bring profits.

I found in header.php and a few others stupid lines like <?php UPLOADED by Sn3ak3r;> etc. so I cleaned it.

But I cannot sleep tight as I think something more could be there, deep somewhere in WP files.

So my questions are:
1. What I should check? It take a while to scan manually all files and look for funny looking scripts or suspicious div lines.

2. What extra steps I can take to be more safe?

3. Is it possible that someone can get into my hosting files (other than on my website) or to database by content hided in nulled theme?

I followed steps in this topic:
http://www.blackhatworld.com/blackh...78-amazing-tools-detecting-hacked-themes.html

Seems like those online scanners didn't find anything but they also didin't show me those extra added lines "uploaded by ...... ", they weren't visible on the website but we know that spiders and robots scrape all this shit. I really want to get rid of this.. :sgrin:

I will be appreciated for good advice.

ItsHere

i won't use nulled again. 3 times using nulled and nothing works good in long time. most of them attacking when my blog has stable visitor. one of them build link farm, other detected as virus.