1) When isolating a single limp, would you use your regular opening ranges?
For example someone in MP limps and KJo/QJs is towards the bottom of your opening range from the Hijack, would you still iso with those hands or tighten up a little?

2) I read somewhere that I should try to play between 15-20% of hands, but what does this look like from each position? Is this 5% from UTG up to 50% from the button. How do I make sure I'm hitting around these numbers with the pre-flop ranges I'm using.

1) In general, keep your standard opening ranges. A limper is more often than not a completely clueless player aka fish and so you will be raising the limp for value with those hands. They will often be limping with hands like K2s, T7s or other trash which you are doing great against.

2) I'd recommend you focus less on the numbers and more on the hand ranges per position. If you are playing the right hands from the right positions, the numbers will tend to be close to the recommended values. There are hundreds of starting hand charts online so you can just find what works for you. Note that the action before you and the opponents you are facing should affect your default starting hand ranges.

well in my case i take the decision depending my intention on the hand.

i would def iso with KQ OJ JTo but it depends on who is on the blinds, if i have a monkey 50vpip or a caller 25vpip whats the point even trying, since most of times you will atleast get the call from the limper, and since it's micros you will atleast hit one or two cbets to end the job. but then it comes to ranges if you want to do that.

it also depends on the position, the size, the number of limpers etc.

on the 2nd im with Antonio pick a range, and then check in your reports what hands are you winning with and what are you losing with, and then see what you did right or wrong to adjust.

I took a look at the ranges for curiosity sake and they recommend a significantly wider RFI range from the SB (47.8%) than the BTN (40.6%), which makes me think I'm taking crazy pills..... If someone is opening half their hands from the SB vs my BB, I'm going to be punishing them for that. Maybe the villains I play against suck at uNL, but I am having a hard time wrapping my head around the idea that opening wider from the SB than the BTN vs a competent (or semi-competent) BB can be good.

Depends on villian. If they fold to flop cbet 75%+ and vpip >40 then u can raise atc from the blinds. If they dont fold much to cbet then you want to have a hand that is value vs their range, so like K8o should be good. Don't forget who is acting behind you, are they nit are they aggro etc.

1. single limp, depends how often they limp. i
If they are limping 40%, no change, if only 14% then yes adjust.

2. Learn a standard range of around 14% hands and adjust up and down depending on your position. You basically want to learn your preflop ranges and have it have good % for each position. At lower stakes you can get away with bigger ep range due to low 3 betting % in general.

14% - A2s+, KTs+, QTs+, 76s+, AKo, AQo