It takes a while for Google Webmaster Tools to update the amount of links sent by sitemap. I was wondering if updating it on a daily basis could delay it even longer or actually help. The slow indexing may be caused by the low pagerank, which is 1.
I think you're confusing multiple variants here.
If you add your sitemap in Google Webmaster Tools, it will process and update within 5 minutes. It doesn't mean that all the URL's included in your sitemap will be indexed nor does a sitemap instruct a search engine to index the URL's in a sitemap. A sitemap is only required if your site possesses complex internal linkage and structure of hierarchy otherwise, there is no real need for one.
Google Webmaster Tools isn't real time nor is known for being particularly quick to update, it can take a number of weeks for Google to crawl a site, then for the algorithm to work it's magic before Google decides what to index and cache - all this occurs before you will see your website appearing in Google's index - of which you can test by using the following in Google's web search:-
You would only need to update your sitemap daily if you have a lot of new content being published daily. If you don't then there is no reason for a search engine to revisit your site that frequently, and as such, you shouldn't attempt to get their crawlers to do so.
Your website should dynamically generate your sitemap based on it's content, this then only requires to be submitted in Google Webmaster Tools the once. It will continue to fetch the sitemap and update providing your hosted sitemap is getting updated.
Websites can take weeks to index, the best approach you can take is to link to your site from somewhere on the web - even from Twitter or Google+ has resulted in indexation within a matter of hours. What you refer to as "slow indexing" may not be particularly slow at all. Using the query above, replacing domain.com with your domain, do you have any pages indexed at all? If not, how long has it been since your website went live?
If your site has a PageRank of 1, then it is highly likely to be indexed and been online for some time, in which case, there is probably some more serious issues onsite preventing crawling/indexing of your site if you feel this is slow. Something we can't really elaborate on without seeing your site. PageRank has no direct relation to indexing or ranking - it is purely a very basic metric of authority which can be up to three months out of date / inaccurate.
I hope this clears up some of the confusion...
In short, link to your site from somewhere in the public domain, monitor indexation, if there are issues with content getting indexed, review and analyse your site. What Google Webmaster Tools is doing is irrelevant to your site's performance in Google Search.
Unless your site layout is actually changing, you're not really doing anything constructive.