Planets maximum loyalty depends on it's distance from your capital planet. If you hover your mouse over the loyalty percentage, you can see the planets distance  from your capital planet, and maximum loyalty (that includes the 10% attainable with culture). 25% is minimum, that can rise to 35 with culture (yours or your ally's). On larger maps you have to relocate your capital to rise loyalty on border worlds. Also enemy culture lowers your planet loyalty.

it will, but you might find a place where the overall loyalty would be higher. if for example your homeworld is at the edge of the map, then relocating it to the center would profit the far off colonies and would not overly impair the ones that were closer, because they are still fairly close. it depends on the case, but more often the relocation won't be utterly dramatic, maybe 2 - 3 jumps from your original hw.

so again, it could lower the allegiance of the worlds near your original hw, thus pick your new one carefully.

you can also buffer the max loyalty with things like that one thing thats one the last tier of the advents culture research tree or the advent starbases induced reverance ability

well thats if you play advent anyways

yes but are there ways to do it with out mod/hacking the game besides what i mentioned earlier

I thought that too.  That's why I came in here to have a peek.